A mouthbreathing illiterate moron's mishearing and subsequent misspelling or mispronunciation of the word "comeuppance." The combination of "cum" and "muffins" adds hilarity to the usage of the term, as the word is typically placed in the syntax as an object to be received, as a result of karma, by a person perceived to have committed a wrong.
Yeah, that assholescrewed my best friend after I loaned him 400 dollars, but sooner or later he's going to get his cumuffins.
What someone would receive after insulting a baker. Similar to that of getting comeuppance, except this involves a baker using less cowmilk and more manmilk in the muffins.
Some guy: Hey baker! You and your buns can suck it!
Baker: How about a free muffin to change your mind?
Some guy: Fine, we'll see
(Om nom nom)
Some guy: WTF? Salty muffins?
Baker: Them be some cumuffins mothafucka!
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"