When, at a house party, the bathroom line becomes noticeably longer than it usually does, it it because someone is in there taking a huge crap that couldn't wait until later. Or maybe he was too stupid to clear his colon beforehand. Either way, when the perpetrator leaves the bathroom, the entire place stinks to high heaven.
Guests: Party shit.
Example 2: Jeff: It looks like they left an 'r' off your "party shirt".
Steve: No. They didn't.
Example 3: Mark: Why does it say "Party shit" on these cocktail napkins?