Had to be someone's sense of Black Humor. However, it does appear erratic and not like a chisel or dremel type of defacing. No repetition that I can see.
Impossible , but it looks like bite marks, part of a molar impression up by the hairline and on the temple, near the L is the eyetooth which hangs down lower. even looks arched.
To determine whether or not this is a genuine error, you'd need to watch the McGruder film frame-by-frame for at least 40 years. Then you still wouldn't know. Was it minted on November 22? My apologies to the squeamish.