Quoted from Joystiq: If you haven't gotten the note about Portal yet, well, it was a HUGE SUCCESS. We can't really overstate our satisfaction and for those who would like to hear the song from the finale sung by the original creator, Jonathan Coulton, we've got one video above and another after the break. Just to reiterate, the song does give away plot points -- but seriously, finish Portal already, it's done in an afternoon.
The video above is from a concert in Atlanta and the one after the break is from the AT&T channel when they visited Coulton at his home studio in Brooklyn. Spoiler Alert: Oh, the AT&T people also feed Coulton cake, but there's something wrong with it -- and, no, it's not a lie.