this is "nightline." >> tonight, showdown in sin city, donald trump and his republican presidential rivals take the stage in vegas and only 48 days before the iowa caucuses. what the candidates had to say to a nation jittery about terrorism and the moment between trump and jeb bush when the gloves came off. >> donald, you're not going to be able to insult your way to the presidency. what has four legs, a wet nose and more instagram photos than humans? what they are finding massive fame online and raking in big bucks. and behind the scenes of "star wars," the moment they found the franchise's next leading lady. and which one of the original cast members was known to get down during the on-set

dance parties? >> it's true. all of it. >> but first, the "nightline five." >> there's something out there. it's a high youly contagious disease. it can be especially serious, even fatal to infants. unfortunately many people who spread it may not know they have it. it's called whooping cough, and the cdc recommends everyone, including those around babies, make sure their whooping cough vaccination is up to date. understand the danger your new grandchild faces. talk to your doctor or pharmacist about you and your family getting a whooping cough fashion nation today. number one in just 60 seconds.

donald trump rolled in to vegas tonight with the most to lose. the clear republican front-runner knew he had a

target on his back heading into this, the final debate of the year. but he was not the only one who took fire. here's abc's david wright. ♪ >> reporter: the las vegas strip hosts plenty of prize fights but tonight at the venetian this one was big even by vegas standards. and bloody, even if most of the prize fighters wore dark suits, red tie, and a flag pin. >> am i talking or are you talking, jeb? >> i'm talking. >> you're not talking. you interrupted me. >> reporter: tonight jeb bush showed up for the fight, landing some punches on front-runner donald trump. >> donald, you're not going to be able to insult your way to the presidency. that's not going to happen. i do have the strength. [ applause ] leadership -- leadership is n not -- leadership is not about

attacking people and disparaging people. leadership is about creating a serious strategy to deal with the threat of our time. >> with jeb's attitude we will never be great again. that, i can tell you. we will never be great again. >> reporter: this was the last gop debate of 2015. the first run, since the terror attacks in paris and san bernardino, also the first gop debate since donald trump vowed this -- >> for a total and complete shutdown of muslims entering the united states until our country's representatives can figure out what the hell is going on. >> reporter: tonight as expected -- >> border security is national security. and we will not be admitting jihadists as refugees. >> reporter: terrorism and trump were both center stage. >> donald, you know, is great at the one liners. but he's a chaos candidate. he would be a chaos president. >> jeb doesn't really believe i'm unhinged. he said that very simply because

he has failed in this campaign. it's been a total disaster. >> reporter: bush wasn't the only one gunning for him. rand paul took some shots, too. >> the question is, how do we peep america safe from terrorism? trump says we ought to close that internet thing. the question really is, what does he mean by that? like they do in north korea? >> reporter: trump's reaction to all of these attacks spoke volumes. at one point trump actually blamed cnn for egging bush on. >> i think it's very sad that cnn leads. jeb bush, governor bush, down a road by starting off virtually all of the questions, mr. trump this, i think it's very sad. >> if you think this is tough and you're not being treated fairly, imagine what it's going to be like dealing with putin or dealing with president xi or the islamic terrorism that exists. this is a tough business run for president. >> you're a tough guy, jeb. >> we need to have a leader.

you're never going to be president of the united states by insooting your way to the presidency. >> let's see. i'm at 42% and you're at 3%. so far i'm doing better. >> i was surprised at his aggressive attitude toward donald trump. i thought it important he be more awe gresive and assertive but i thought he would have aimed at others. >> reporter: dr. ben carson treated like a front-runner last time around, this time he struggled to get a word? >> some people say you're weak because you're not loud and you're not rude, but the fact of the matter is, look and see what i've done, and that speaks volumes about strength. >> i think that probably the thing that came out of this was a continual slide of ben carson who led at one point in time and afterward the tragic events in france when people started focusing more on these issues related to security he started falling. i think the course of this debate that fall continues. and my expectation is ben carson will be in seventh or eighth place by the next couple of weeks. >> reporter: the ratings of

these debates have rivalled prime time tv shows and sporting events. >> i think we've run out of red ties in the las vegas area. >> reporter: tonight in queens the qed cafe had it on big screens. >> think about what you did, marco. >> reporter: comedians and commentators weighing in in realtime on the action. >> jeb start looking like when george won the presidency and he realized he was never going to be as good? >> it's almost like watching wwe at this point. i think that's the appeal of donald trump, is that it's like watching macho man randy savage with, you know, even worse hair. >> reporter: throughout the campaign trump's fiery rhetoric hasn't exactly hurt him. quite the contrary. but senator ted cruz has been gaining ground, several recent polls show him slightly ahead of trump in iowa. until now the two have mostly abided by a mutual nonaggression pact. >> you better not attack.

>> reporter: even tonight cruz studiously avoided a full frontal attack on trump's proposal to ban muslims from the u.s. >> everyone understands why donald has suggested what he has. >> reporter: though he did distance himself from it. >> there are millions of peaceful muslims across the world and countries like india. it's not a war on a faith. it's a war on a political and theocratic ideology that seeks to murder us. >> reporter: the turmoil up top has left the rest of the field to jockey into position themselves as the reasonable alternative. tonight senator marco rubio tangled with ted cruz over immigration. >> does ted cruz rule out ever legalizing people that are in this country illegally now? >> senator cruz? >> do you rule it out? >> i have never supported legalization and i do not intend to support legalization. >> reporter: their conflict sounding at times like a vice presidential debate, auditioning for the second spot on trump's ticket. >> we will build a wall that

works, and i'll get donald trump to pay for it. >> i'll build it. >> reporter: governor chris christie painted himself as a seasoned executive but he may not have helped himself with women voters with an analysis of today's terror scare in l.a. that sounded straight out of "father knows best." >> think about the mothers who will take those children tomorrow morning to the bus stop wondering whether their children will arrive back on that bus safe and sound. think about the fathers of los angeles who tomorrow will head off to work and wonder about the safety of their wives and their children. >> reporter: does any of this have the potential to change the race? >> i think donald trump comes away as still the leader. and i think ted cruz and marco rubio are the people closest at his heels. i think jeb bush tried in his way to be aggressive tonight but i think it's probably too little too late. >> reporter: voters at the qed screening party tonight aren't sold. >> i really couldn't pick a

winner. lost me halfway through. >> reporter: as of tonight, there are less than 50 days to go until the iowa caucuses. soon enough that voters there will have their say. i'm david wright for "nightline" in new york. next, don't be fooled by the frown. this cat is rich. how pets are big business on the internet. and behind the scenes of "star wars," the force awakens. the painstaking work of creating the next generation of storm troopers and droids. i took mucinex dm for my phlegmy cough. yeah...but what about mike? he has that dry scratchy thing going on. guess what? it works on his cough too. cough! guess what? it works on his cough too. what? stop! don't pull me! spoiler alert! she doesn't make it! only mucinex dm relieves both wet and dry coughs for 12 hours with two medicines in one pill. start the relief. ditch the misery. let's end this.

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i post pictures of my cats

all the time on the internet and nobody has ever paid me for it. apparently if you're smart about it you can turn your cat or dog into a cash cow. here's abc for a special series "social stars." >> so cute. >> don't be grumpy anymore. you're super cute. >> aw. >> reporter: it's her frown that has many cracking a smile. >> grumpy cat. >> i love a good photo shoot, especially with such a famous star. >> reporter: she's known as grumpy cat. but her real name is tarter sauce. >> nice. >> reporter: and it's her signature frown that went viral three years ago and helped create what's now a booming grumpy cat industry. >> there was a swarm of people around grumpy within seconds of you taking her out of the bag. she handles all this fame so well. >> she's a diva. >> she was born star.

>> reporter: 30-year-old tabitha is grumpy cat's human. >> i've definitely been happy doing it the last couple of years. >> reporter: in the last two years over 250,000 grumpy cat calendars have been sold. her book has been translated into 15 languages. the grumpy plush dolls so far, 1.5 million sold. she even has a leading role in her very own lifetime movie. >> are you serious? >> i'm serious. look at my face. >> i think sometimes humans tend to shun people that don't always look the same. >> honestly, i think you're right. like grumpy cat kind of makes being different okay. >> reporter: and advertisers are taking notice, signing the viral kitty to mega deals. from fridays i cans -- >> grumpy cat could not care less. >> reporter: to cheerios -- >> not even a smile?

uh. >> she's so cute. >> never thought i would be m l managing a business around a cat. it's definitely fun and interesting. >> reporter: that's brian, tabitha's brother. he's the man responsible for taking and uploading the photo that shot grumpy cat into the spotlight in 2012. that same photo, a mean sensation, shared thousands of times around the web, brian is now grumpy's business manager. >> i used to work for the cable company and i left that about a year and a half, two years ago. and this is my full-time gig now. >> full-time grumpy cat. >> definitely. >> reporter: a petite four pounds three ounces but it's not just her underbite that causes that iconic frown. it's a unique genetic position. >> tell me about this disorder. >> feline dwarfism, it's genetic. it's basically like human

dwarfism. it just makes them little. >> reporter: these days pets are big celebrities, too. they even have their own version of the oscars, the golden collar awards. >> thank you so much. >> reporter: which is awarded a-list pets like uggy, star of "the artist," and can't turn the channel without running into these small yet huge celebrities, taco bell, target, even budweiser. but in the dog-eat-dog world of entertainment, social media is making it easier for pets to become instant celebrities. for example, cloe, the mini frenchy who was discovered on instagram. >> her posts tend to make people smile and laugh and feel good. and i think translating that to a marketing initiative and a partnership with a brand is so powerful. they want their ads to have that same effect. >> reporter: that's cloe's owner. >> i think six months. it really started taking off and getting brand requests every

week, everything from "vogue" to jimmy choo to dyson wanting to work with her that it became a little more serious. i set up an llc for her and now she has her own company. >> reporter: the more influence they have online the more money they can make. >> it can be anywhere from a couple hundred dollars to a post to $30,000 for a post. it's a wide range. >> reporter: the demand has grown so much that come january she will be fully dedicated to managing a pet model agency. >> it takes a lot of time. that's definitely one thing i think people may not realize. bringing her to all of these events and appearances and photo shoots. and so you need to have time to do it. >> reporter:s a for tips that can make your pets the next internet sensation -- >> think the content people want to share. if something makes you laugh, makes you smile, you want to share it with everyone. oh, my god, look what i saw. so content that does that, i think, is the trick. >> reporter: there's no denying that these pets and their owners are making a living.

how much exactly? well, grumpy cat's owners won't say. >> it has to be really unique for your family because now this is like your full-time job. it's your brother's full-time job. >> yeah. >> this is how you're making a living now. >> yeah. it's really awesome. i'll say maybe grumpy cat brings home the cat treats. >> yeah. >> and she's definitely priceless. lives pretty comfortable. otherwise, we don't talk money too much. >> reporter: one thing for certain, this feline phenomenon is far from over. do you have the energy to do this for the next 14 years perhaps? >> i hope so. i have a daughter, so she's going to keep me going if not grumpy. >> reporter: after all, nothing says you've made it in hollywood like your very own replica at mad mad mad madam. for the record i did meet once meet grumpia cat. this is you us on the set of gma. i can tell you that she is nicer than she looks.

up next here on "nightline," "star wars: the force awakens," why they thought he would make the perfect villain and why the whole cast and crew is talking about harrison ford's dance moves. (dramatic music) centrum brings us the biggest news in multivitamin history. ( ♪ ) a moment when something so familiar becomes something so new. (impact on metal) introducing new centrum vitamints. a multivitamin that contains a full spectrum of essential nutrients you enjoy like a mint. new centrum vitamints. go to centrum.com for a $4 coupon. new centrum vitamints. innovative sonicare technology with up to 27% more brush movements versus oral b. get healthier gums in 2 weeks guaranteed. innovation and you. philips sonicare

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. geeks all over america are dusting off their costumes and getting ready to line up for the opening on friday night of the new st"star wars" movie and in preparation, abc chris connelly sits down with the creators of this reboot.

>> monday night in hollywood, the world premier of "star wars: the force awakens." it's action and humor. it's new characters and lightsabers. >> it ends up being a story of adventure and loyalty and shock and surprise and uses this amazing and precious thing called the force to tells us how we're all connected. >> reporter: so much of it the work of producer kathleen kennedy and director co-writer j.j. abrams, all of it inspired by "star wars" creator george lucas. >> there isn't a day that goes by or went by that we were making the movie that we don't talk about george. you know, it is -- it's the standard what would george do. >> the thing that is most remarkable is that george got everything right. >> reporter: vet an of "alias," "lost," "mission impossible 3" and the "star trek" series and now 49-year-old abrams was brought on the "star wars"

franchise by kennedy. for decades top producer on steven spielberg's acclaimed films. >> i did pose this provocative idea of who is luke skywalker that that would be something that was said by one of our characters. >> why was who is luke skywalker such a fascinating question? >> i guess because it spoke to a new generation. it was that idea that there would be young people for whom luke skywalker was essentially a myth. >> reporter: in crafting and setting thes for awaken, abrams wanted the characters young, even bad guys like ky. >> he's like, adam driver, really? mike drop. >> one of the things that we talked about very early on was that the villain in the movie be young. he's in the midst offed a less 70 angst. >> that's new because there's a lot of male pattern baldness in the villains in previous "star

wars." >> you were right about me. >> reporter: months of auditions yielded the lead. john boyega was cast as the exstorm trooper fnn while daisy ridley was chosen for rey. >> when she came in and read you just know. and literally i had to not giggle too loudly from behind the camera because i was amazed at what she was doing. >> reporter: to ease the stress, each week the entire cast dancing. >> it was this dance craze. then we all got onboard. by the end, there were like 200 plus people, including harrison ford. >> infront of the falcon. >> reporter: abrams hoping this film will have the same emotional punch that the 1977 one had on him as a child. >> the thing i felt when i was a kid when i left that theater was the world was huge. and to have people, especially kids, go to see the movie and see themselves in it a