A party to exorcise an evil and nasty person from your life can be humorously referred to as a "toxic exorcism" or a "negative energy cleanse." While not a formal concept, it symbolizes a gathering aimed at celebrating liberation from toxic relationships. Participants might engage in activities that promote healing and positivity, effectively "banishing" the negativity associated with that person.
A person who thinks nasty things could be described as pessimistic, cynical, or having a negative mindset.
party animal
You could call them a party animal. The life and soul of the party opposed to a party pooper.
Party Pooper
You could call them a party animal. The life and soul of the party opposed to a party pooper.
The Host
Host
Guest of honor
The host or hostess.
If I understand your question a posed, the following answers apply: 1. The "calling party" is the person/phone who/which initiated the call. 2. The "called party" is the person/phone who/which answered the incoming call.
A gatecrasher barges in without an invitation.
A person who sets up an event is called a party planner