LOL I can't believe I made you do a remix bid without knowing what one is! whoops. there was a whole remix challenge at vvc, I think in 2007. I'll find you some links later on. typically a remix bid takes up similar themes but uses a different song - the cover was just serendipitous.

and yes, mashups are sort of a joke thing where you just swap in different audio. they can be amaaaaaaaazing.