Attend a party without being invited. You just show up. It may be a party thrown by someone you know or a complete strangers house. Sometimes people don't mind that you came to their party, but sometimes, your presence will be unwelcome and you may be asked to leave. The fun of it is you don't know until you get there what the reaction will be. If you crash the party, be ready to accept the consequences.
Dude, there is a jamming party down the street! Let's go crash the party!