VGFacts

Here's a pretty "hidden-in-plain-sight" trivia:
The "Slider" Theme and "Snow Mountain" Theme are both variations of the same song played at different tempos and with different instruments.

Proof:


They even have similar lengths, both clocking in at around 3:35.

And as both game4brains and the Mario wiki inform me, they're both variations of the music played in Bob-omb Battlefield, which is referred to in Super Smash Bros. Brawl as "Main Theme Super Mario 64".