Mad Men: the musical

Mad Men is so dense, and well-acted and made that it's easy to forget that Don, Betty, Pete and co aren't actually real. So much so that seeing the actors out of character can be discombobulating. So the sight of the entire cast of Mad Men (well most of them) along with the cast and crew boozily singing one of series three's key numbers Bye Bye Birdie in a leaked video (made to thank creator Matt Weiner) is odd one to behold. Peggy with a BlackBerry! Bert Cooper in a T-shirt! We're not sure if this is the best thing we've ever seen on YouTube. Or the worst. Your thoughts please …