After a night, in which occupants of an abode have been having messy sexy with their respective one night stands, they all miraculously meet at the washing machine (in the morning) to wash their sheets. This event can also be promoted to other housemates by the yelling of "Sheet Party!" as one occupant departs for the laundry. This often leads to a bedroom exodus by the other occupants who wish to also join in the "Sheet Party" and swap stories.
"Sheet Party" can also be proclaimed by an individual prior to intercourse if a sheet party is highly likely.
"Yesterday was a massive Sheet Party"
Yelling with head poked through the door "SHEET PARTY!!" followed by cheers and laughter from fellow housemates and confused looks from the unsuspecting victim.
"How was last night?"
"Mate, it was a Sheet Party"