Party extras at Patchy's party consist of writers of the show, including producer Paul Tibbitt.
The real title of this episode is called, "Party Pooper Pants", but most airings and releases just go by "SpongeBob's House Party."
When SpongeBob and Patrick throw Patchy's invitations into the fire, it is one of the many times where fire is shown to exist underwater. This was ironically alluded to before when SpongeBob complains that the sender doesn't care about the limitations of living underwater.