2) An exclamation of surprise from something "most unexpected."
Derived from a 1994 episode of The Tick animated series entitled "Heroes."
intr.v. roofpigged, roofpig·ging
Originally derived from a quotation in '90s cartoon television show "The Tick" in which the eponymous hero, upon seeing a pig on a rooftop, exclaims "Roof Pig! Most unexpected!".
She was acting so strangely the other night - a total roof pig.