Taken from the hit sitcom "Family Guy," this phrase can be said to anybody who either kills a joke, makes an uncalled for comment, or otherwise just needs to be ridiculed spontaneously.
Steve: "I think that octoberfest might be the best beer ever."

Bobby: "I agree"

Jeff: "I think beer is disgusting no matter what it is."

Steve to Jeff: "Shut up, Meg."
by whitey McRosenski September 18, 2010
Phrase normally used when some dick says something stupid
at an irrelevant time, and/or say's a joke that isn't funny
in any way at all.
*in the middle of a silence*
James: Hey guys! Check this out!
John: Shut up Meg.
by haz98 August 17, 2012