It's called the Turnip Glitch.
http://kriptikclan.com/turnipglitchexplained.wmv
This video explains how to use the turnip glitch.
http://www.kriptikclan.com/turnipglitch.wmv
This video shows more examples of using the turnip glitch, including the game freezing all together.
However, I myself have used this glitch and haven't found any "garbled" text and whatnot. It looks like I can't seem to unlock the glitch characters.
*Only works in the first version of the game.*