When added to most any verb, the suffix "ems" puts that verb in to action in place of a longer, less necessary sentence/predicate. Able to be used in the 1st or 3rd person, this suffix typically makes light of a more serious situation, however the particualar usage of this suffix in often left to be interpreted by the listener according to the context of the conversation or mood of the room.
Upon winning the sports bet, Mitchell screams "Payems"; short for "Fantastic, I have won this bet and will be paid". When Tyler is asked if he should go back to the bar and pay the tab that he forgot to pay, Tyler screams out "Fuckems"; short for "Fuck that, I will do it later". Brantley points out the attractive girl at the BBQ restaurant by simply saying "Doems"; short for "I sure would like to do her/sexually intercourse her".