What the Funky Monkey- Used by those who do not wish to offend conservative, religious, or old people. It is a suitable exchange for the expression WTF
Jason: Dude, all the people are like flying, so are you!
Freddie: WTFM?
A person pretending to be something they aren't, or an impostor. This is inferred because of the old alien movies where alien pods appear on earth and the "pod people" dispose of the humans and slowly reproduce the bodies, pretending to be humans.
The pod person was pretending to be my father, but I knew that he was an alien when he acted differently than my father ever would have.