I know someone who did the whole 'invite 150 people, tell them they can bring plus ones if they ask'.
They didn't ask. Share share share. Invite friends, tell friends. Around 500 people turned up.
Some of them were groups of boys/girls who had no connection to anyone at the party, genuinely. Still baffled at how they heard about it.
The number and amount of police vans, ambulance vans, vomit, cigarette butts, empty bottles and used condoms at the end of the night was the very definition of horrific. I'm surprised they didn't have to tear down the house.