Stick it in a muffin (also phrased "place it in a muffin") basically means shut up, stop, yeild, do not continue...
Brittany: "Hey did I tell you about my date with Brad?!"
Lucille: "About a million times. Please, stop talking about Brad."
Brittany: "So, we went out to the movies, and-"
Lucille: "Gosh, Brittany, STICK IT IN A MUFFIN ALREADY!"
A term used to describe some one extremely cool who likes fall out boy and hot topic (and their names normally start with a A or K)
some one: "hey, did you see any super-saur guys at the mall?"
some one else: "nope."
some one: "hey look there goes Alexis the Super-Saur!"
some one else: "OMG I wish I was her!"