"Party pooper" is a colloquial term used for a person who ruins fun, often by being overly critical or negative. Antonyms for this term could include "life of the party," "fun-lover," "optimist," "enthusiast," "cheerleader," "reveller," "jovial individual," "celebrant," "pleasure-seeker," "party animal," "burst of energy," and "joyful participant." These individuals are known for bringing positivity, energy, and excitement to social gatherings. They are often the ones who lift the spirits of others, make jokes, initiate games, and create an overall fun and enjoyable atmosphere. Unlike party poopers, these individuals are cherished, and everyone loves to have them by their side during celebrations.