I've seen it done before. One of my friends freshman year in college had played Contra for nintendo so much that I literally saw him beat the first 3 levels with a blindfold on and looking down. It was freakin awesome. I tried playing my claim to fame, (Mike Tyson's punch out) but it didnt exactly work correctly, I was only able to beat Glass Joe because, well, he's glass Joe.
Have beaten the game straight through a number of times however, and that is why I am lord of punch out.