Cupid's Mansion is a large residence in Fairy World where Cupid resides. It first appeared in "The Big Bash".
Cupid dwells in a mansion somewhere in Fairy World, and he occasionally hosts a party for godchildren where he hosts a scavenger hunt, which is really just an elaborate ruse to get them to do his grocery shopping. The mansion also has a secure glass container guarded by love birds, monstrous (but easily distracted) bird creatures, which Cupid uses to keep his bow and arrow safe, and from anybody could not steal from it
Cupid's mansion was featured prominently in the episode "The Big Bash", where Timmy and Remy encountered each other before setting off for the items listed in Cupid's "scavenger hunt". The winner of the hunt gains some rule-free wishes. After learning they were tricked by Cupid into doing his grocery shopping and that there were no rule free wishes, Remy and Timmy team up against him and swear a (temporary) truce between each other. They then had their godparents poof up objects from the past and ordered them to get Cupid as payback. After that, Timmy and Remy enjoyed the food that Cupid was going to eat for his brunch while Cosmo and Juandissimo were chased down by objects created by Wanda as payback towards Cosmo and Juandissimo for using Wanda and a nickel as part of a bet(since Cosmo betted her for a nickel though he claimed it was really shiny).
The mansion also appeared again in "Stupid Cupid" where Timmy visited Cupid to try to get him to shoot Trixie Tang with a love arrow so that she would fall in love with him for the school dance. Cupid refused, and then left to go on vacation, but Timmy managed to steal the bow and arrow anyways. However it backfired on Timmy many times, causing other people he knows and/or loves to fall in love with someone they don't really love. Timmy is then forced to get Cupid's help to undo the mess. Cupid does so, but this also causes Trixie to no longer love Timmy. As punishment for stealing his bow and arrows, Cupid forced Timmy to do his laundry.