Due to the game's popularity, many Pac Man cabinets were actually bootleg boards. Some of these games had differences and modifications which could explain some myths. (Such as the "gold bar" or "edible eyeballs" below.)
In 1982, an 8-year-old Jeffrey R. Yee of San Fransisco set the worldwide record for the high score on Pac Man: 6,131,940 points.
This is impossible. The highest score achievable in Pac Man is only 3,333,360 points, due to a game-ending byte-overflow bug in the screen rendering code when level 256 is reached. This causes a "split-screen" effect, rendering the game unwinnable. Even then-President Ronald Reagan was fooled by this lie; he sent Jeffrey a letter of congratulations.
Golden bars could be found in-game on some machines, but not others.
Finding the golden bars and their accompanying screwdrivers would net the player millions of points.
It was possible, on later machines, to gobble up the eyeballs after eating a ghost.
This is believed to be a lie and world wide hoax, just ask anyone involved with Pac Man.