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1.
Noun. Metaphoric phrase most commonly used to describe a highly unusual or unforeseen event or occurrence. Can be extended to describe people who are not as they first appear, or when a person acts out of character.

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!".
Wow! Saints won the Superbowl? That's one heck of a roof pig!

She was acting so strangely the other night - a total roof pig.
by FightingTorque May 12, 2010
 
2.
1) An object that catches one off guard by being out of place.

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
Roofpig! Most unexpected!
by Unorigional November 15, 2004