The Subway surprise, as it were, is a phenomena associated mainly with homosexual men. It is the act of inserting a clear plastic tube into
one's anus. Then, a partner slides the other
end into his ass. then, partner
one defecates into partner two ass, the turd representing a subway
car slipping and sliding into the next chocolate train stop. Sometimes, the duo rocks back and forth, sliding said turd between each other.