The ones nobody invited to the party, but who hang around anyway - no-one will ask them to leave, as no-one knows who invited them in the first place.
You: What's up.
Randomer: Hey, not much, you?
You: Nice, not much.
Randomer: Cool, later.
*You both leave the lockers and forget about each others' existence*
Sane Person : Stfu, you complete & utter idiot.