This is the song from the end credits of the PC video game Portal, a puzzle game built off of the Half Life 2 engine. The song makes much more sense if you have actually played and completed the game, but every time I hear this, it gets stuck in my head for several days, so I figured why should I be the only one to suffer?
Anyway, in the game you go through several tests, most of which involve the use of a gun that creates portals. At the end of the game, you fight a robot who’s been monitoring your progress and making snide comments at you the whole time. The robot is the one singing the song. Probably the catchiest and funniest song from a video game ever. Written by Jonathan Coulton. Enjoy!