kids-- and parents-- loved jim henson's muppets. >> girl: 8, 9, 9, 10, 11.. >> kermit: so do you. >> stahl: and testing showed kids who watched were learning. sometimes the lessons were about real life-- >> mr. hooper: i'm your neighborhood friend, mr. hooper. >> stahl: as when the actor who played beloved shopkeeper mr. hooper passed away, and the show decided to address the subject of death head on. >> big bird: tada! >> adults: oh, look at that. >> big bird: i can't wait till he sees it. say, where is he? >> stahl: you could have changed actors. >> ganz cooney: yes. but we decided "sesame street" had always dealt with the real. and it was real, so we decided not to just replace him and call the man mr. hooper and hope they didn't notice. >> maria: uh, don't you remember we told you mr. hooper died. he's dead. >> big bird: oh yeah, i remember. well, i'll give it to him when he comes back. >> susan: big bird, when, when people die, they don't come back. >> big bird: ever? >> stahl: over the years, "sesame street" did segments about other challenging subject