Le Cochon Danseur (the dancing pig) is a film oddity from 1907, based on a vaudeville act, which stars a lascivious pig headed fellow with eyes for the young lady with whom he shares a stage.
According to Know Your Meme, it's the last bit of this strange short that made it so well known:
...most noticed part of the play is the last 20 seconds, showing the pig flailing his tongue and laughing showing his sharp, scary teeth. Most people thought this was rather disturbing and focused mainly on this part because of it. Other then that, the rest of the clip is the pig winking and boggling his eyes in strange ways
Sounds like this little piggy skipped the market and went straight off the deep end!
--via Laughing Squid