This phrase, term, whatever, came from the great Tom Hiddleston, who is either: truly Loki, Loki’s spirit animal, or the other way around.
Example #1
Person 1 (with tray of food): "What, probably around ten bucks right?"
Cashier: "Actually it's already been paid for"
Person 1: "What?"
Person 2: "HEHEHEHEH I BOUGHT YOUR LUNCH FOR YOU! LOKI'D!"
Example #2
Person 1: "Can you believe Joss Whedon's April Fools prank? He never actually intended on telling us what Loki's army consisted of"
Person 2: "I know! He's such a troll! We totally got LOKI'D!"
Something that is really amazing and fantastic whether it be a person,place,thing or idea
Originates From: A running joke within RoboCop is an inane TV show with the catchphrase "I'd buy that for a dollar!", which people in the film's future universe find humorous. The star is the goofy Bixby Snyder apparently based on Benny Hill. However neither the name of the show nor the character are ever revealed in the movie.
A person was watching the super bowl half time show, and Janet Jackson breasts got exposed.