Well I'm not sure what song this is - on this You Tube - will check.
I just remember that in South Park they would play The Forest by The Cure for the Goth Kids.
It's in the episode "You Got F'd in the A" (season 8 episode 4). The one where the South Park kids got 'served.' The goth kids were demonstrating how to dance goth style. The song is a mix of A Forest by The Cure and something else, but it's original to South Park.
It's hard for me to say what's the coolest episode because I love just about all of them. Except for the Britney Spears one.... I can't watch that one, it grosses me out too much.
Okay, South Park. Woodland Christmas Critters. That's my pick. I know, they're all great, but this one just slays me.