A BDSM term used to describe the act of strapping a person to a chair (usually naked) and having them watch Nicolas Cage movies. During the movie the Dom typically plays with the Sub's nipples, thus giving us our name. The original BDSM use was to get the Sub to have a hard on for Nicolas Cage and then to humiliate him for being gay. This isn't a very well used tool in the BDSM community due to people in general having a hard on for Nicolas Cage.
Though it's origins are in BDSM the term has grown to encompass all sexual acts that occur during the watching of a Nicholas Cage movie.
"Dude, what did you do last night?"
"Well I was watching Face/Off with Jenni when she Nippleous Caged me!"
The only real comeback to a so's your face. Makes just about as much sense, but it's a triple threat - it's offensive, confusing, and it draws attention to the stupidity of the phrase "so's your face".
When used, your opponent will be utterly confused. They will either stand with a bewildered expression on their face, or reply with a curt "What?"
At this point all you must do to finish now is go "Yeah! What now?" and walk off with a slight swagger. You win.
This works just about 100% of the time. I'm serious, try it.
Person 1: Alright, that's it. You're an unbelievable douche.
Person 2: Well, so's your face!
Person 1: Well, so's your nipples!
Person 2: ...
Person 1: What now, punk?
Person 1: Will you shut up? Santa does not exist.
Person 2: Your face should shut up!
Person 1: Your nipples should shut up!
Person 2: What?
Person 1: Yeah, that's what I thought!
(as you can see, it works best when you copy the same format the other person used so's your face in)