A person who brings hype and enthusiasm to a party, who helps break the ice so partygoers have a good time.
My university's student newspaper always had wanted ads for 'party pumpers' to work at bar/bat mitzvahs getting the kids dancing and enjoying themselves.
To do shitty stuff that kills everyones buzz at a social gathering is commonly referred to as 'party pooping'. 'Party toilet paper' is any act whereby one who has previously pooped on the party does something totally rad to undo said party poopery and bring everyone's spirits back up to awesomeness levels never anticipated.
me: Did you see that douchebag who pissed in the laundry hamper earlier? What a party pooper.
you: Ya, that was not cool, but then he totally made up for it when he brought that extra keg later! Party toilet paper!
(okay, maybe this term is pretty stupid)
Fogey/fogy /fougi/ sl. (early 18C+, orig. Scot) old-fashioned, stuck-in-the mud.
Person with old fashioned ideas which he is unwilling to change: Come to the disco and stop being such an old fogey!
You think me an old fogeyand an old tory, his thoughtful voice said. I saw three generations since O’Connel’s time. I remember the famine. Do you know that the orange lodges agitated for repeal of the union twenty years before O’Connel did or before the prelates of your communion denounced him as a demagogue? You fenians forget some things. (James Joyce, Ulysses. Penguin Books,1992. p. 38)