Man. I do like a good Portal 2 remix. This one, however, is on another level.
It was created by Will Bedford, and I've been legitimately listening to it all day. Maybe it's the happy pop chord progression. Or the kicky beat. Or the triumphant Cave Johnson breakdowns. Or the double-time section.
Or I don't know, the whole thing. Give it a whirl, you'll see what I'm talking about.
Here's another quick one, called "You Monster." Excellent. Sing it, Cave!