bacpacjac wins the thread for being first, and being discreet about it.
Q1)What was the name of the movie that featured an underground city called "Topeka"?
Ans) "A Boy and His Dog" 1974, directed by L. Q. Jones.
Q2)There were two protagonists. Between them how many legs did they have. Which character was the 'smart one'?
Ans) bacpacjac - "6 [legs]and the shorter one was smarter". A boy, Vic, and his dog, Blood, collectively have six legs. Blood, a dog with a telepathic link to Vic, was the brains of the outfit. Vic ran mostly on guts, boldness, and hormones. The former being his main assets. The last one getting him into trouble.
Q3)Both stars went on to do TV. Name the one who shared character name with a famous American hero in a popular TV show.
Ans) The dog, Blood, got bit parts on TV shows, and several commercials. ,the boy, Vic, was a rather young Don Johnson who went on to play the part of Sonny Crockett on 'Miami Vice'.
Extra Credit - The phrase "Well, I'd say she certainly had marvelous judgment, Albert ... if not particularly good taste" was used. Place it in context.
After Vic, ever horny, went underground following the girl he was captured, hooked up to a milking machine, and used as a involuntary sperm donor. He escapes and returns to the barren surface and finds Blood starved and near death. In the next scene Blood and Vic are seen looking very well fed and satisfied near a fire with a large piece of meat roasting over it. Dog makes the above quote ... the credits roll.
http://en.wikipedia.org/wiki/A_Boy_and_His_DogYou won't learn much of any great practical value from the from it but the movie is pretty much a must-see if you want to understand survival/survivalism and depictions of a post-apocalyptic world as a meme and cultural phenomenon.