Mashup - according to Wiki, it’s a “song or composition created by blending two or more pre-recorded songs, usually by overlaying the vocal track of one song seamlessly over the instrumental track of another”.
Put another way - when you find yourself in the mashup section of Youtube, it’s going to be a long, long night.
If you haven’t heard these, you’re in for a treat.
My top 3.
Can’t decide if you want to listen to the BeeGees or Pink Floyd? Problem solved!
I’ve heard this one a bunch of times and IMO it’s much better then most other mashups in that someone didn’t just take two songs and say “hey guys, I put these two songs on top of each other, wanna hear”. Someone took these songs (BTW, Jump Around is in there as well) and actually spent some time carefully editing them together.