Harpo Marx — my second-favorite Marx brother — explains the origin of the Gookie, his magnificent, world-beating funny-face (there was a fantastic Animaniacs version of this — post links to it in the comments below if you know where it lives online!)
Gookie was funny enough to look at when he wasn't working, but when he got up to full speed rolling cigars he was something to see. It was a marvel how fast his stubby fingers could move. And when he got going good he was completely lost in his work, so absorbed that he had no idea what a comic face he was making. His tongue lolled out in a fat roll, his cheeks puffed out, and his eyes popped out and crossed themselves.
I used to stand there and practice imitating Gookie's look for fifteen, twenty minutes at a time, using the window glass as a mirror. He was too hypnotized by his own work to notice me. Then one day I decided I had him down perfect–tongue, cheeks, eyes, the whole bit.
Over the years, in every comedy act or movie I ever worked in, I've "thrown a Gookie" at least once. It wasn't always planned, especially in our early vaudeville days. If we felt the audience slipping away, fidgeting and scraping their feet through our jokes, Groucho or Chico would whisper in panic, "Ssssssssssst! Throw me a Gookie!" The fact that it seldom failed to get a laugh is quite a tribute to the original possessor of the face.