The extraterrestrial is performed by deliberately (in some cases, nondeliberately) taking a shit on a toilet seat. This may be performed either as an act of revenge or a practical joke.
That asshole definitely stole my Kindergarden Cop dvd so I'm totally gonna perform the extraterrestrial in his bathroom.
Person 1: Hey, Did you hear about the Extraterrestial Life that landed here a few days ago
Person 2: If you mean "Aliens" then yes.
Person 1: Same thing.