Cupid is a minor recurring character on the show, a fairy who is in charge of all things related to love.
He is a fairy whose purpose is to create love all over the world, and it is revealed in one episode that he will die if there is no love. He first appears as a selfish, greedy, egotistical, glory hog who was willing to do anything for money. He lives in his mansion in Fairy World, occasionally hosting a party for godchildren which is really just an elaborate scheme to get them to do his shopping.
Cupid has pink hair and wears a matching pink suit with a bow tie. His wings are slightly different, resembling angel wings rather than the fly-like wings of regular fairies. He has no crown. He also wears a diaper and apparently has a whole wardrobe of them, he also seems to have girly mannerisms.He is also voiced by SpongeBob`s voice actor, Tom Kenny.
Cupid is altogether a fairy, a god, and a holiday character.
Cupid first appeared in the episode "The Zappys!", part of the Oh Yeah! Cartoons shorts. He looks significantly different from his main series self, a large fat floating baby-like human with blonde hair, and is only seen entering the Zappy awards contest.
In the episode "Apartnership", which introduced the new version of Cupid, Cosmo and Wanda had a brief falling out and, in an attempt to get them back together, Timmy found and aimed one of Cupid's arrows toward Cosmo, but Cosmo ducks at the last second to pick up a coin, causing it to hit a chair and fly straight towards Timmy. Timmy ducks and the arrow then hits Cupid by mistake, making him fall in love with the first person he saw. That person happened to be Mama Cosma, whom was trying to get rid of Wanda. He then chases after her right after Cosmo stands up against his mother. The effects of the arrow wore off after the end of the episode.
He would later appear in the first Fairly OddParents Christmas special "Christmas Everyday!" as a member of the other holidays that wanted Santa out of the way due to Timmy wishing Christmas was everyday. He was stopped in the end by Timmy and Santa after the kids from all over the world joined in and caused them to help make things right again.
He later guest-starred in the Valentine's Day special, "Love Struck!", where Timmy wished that all the women were on a different side of the world, while the men were on the same (because in addition to being humiliated in front of most of the girls in his school, Tootie wanted Timmy to be her Valentine so badly). Due to the lack of love, Cupid's energy began to drain away, and he nearly died until Timmy himself used Cupid's arrows and other "love weapons" to make the men and women of Earth fall in love again.