MTV has just announced plans to create a TV series based loosely on George Romero's classic Dawn of the Dead. And they're dodging the "fast or slow" question by doing both: The zombies will start fast, but decay into slow.

What do Alan Alda, Andy Kaufman, and Matthew Perry have in common? They all filmed pilots for failed science fiction sitcoms before doing the series that made them stars. We look at those, and other scifi sitcoms that never were.