Rule #2 says "don't use any copyrighted material".  I'm curious if that would include short audio clips of dialogue taken from YouTube videos.  (For example, a two-second clip of Stephen Hawking's voice taken from a Diane Sawyer interview).  I don't need to include it, but if it's okay for the purposes of the jam, I'd like to.  (I could also do my own bad impersonations, which might fit the theme even better!  Note: the clips would in no way be used to mock anyone).

I think you should probably not do that unless you like probably modify it

Think it would probably be fine. The rule is more for legal reasons. If you think your use of copyrighted material comes under fair use, then it's not a problem really.