Still don't get it. Never mind, it's probably just one of those american things.
It's a line from "Julius Ceasar". He's warned by a seer to "Beware the Ides of March".....meaning he was going to be murdered on March 15.
When the Simpsons were popular, I saw a shirt similar to the pic I posted, which is a close of of Marge Simpson, with the slogan "Beware the Eyes of Marge" under it.
Thought it was funny.