CVG has made an interview with Jonathan Coulton, the lyrical genius behind Portal's final number. Some mild spoilage may occur...
CVG: How did you get involved with Portal?
Jonathan Coulton: I was playing a show in Seattle, and a couple of the game designers came up to me after to introduce themselves. They asked if I'd ever be interested in writing music for Valve - I've always been a huge fan of Half-Life, so I said yes immediately.
A while later we got together to talk about what we were going to do, and it became clear quickly that the character in Portal was a perfect overlap of our sensibilities.