Sometimes abbreviated as "Dr. Killjoy." Coined by N.E.R.D in the song "Anti Matter." A Doctor Killjoy is someone who makes it their business to ruin, take large dumps on, and/or "shoot up" your party or the party you are attending.
Person 1: Haha, I just pooped on your carpet, man!
Person 2: Why you doctor Killjoy, shooting up the party?