Like all Anti-Fairies, Anti-Cosmo has the opposite personality of Cosmo, being very smart unlike his opposite.
He is voiced by Daran Norris who also played the regular Cosmo.
Like all Anti-Fairies, Anti-Cosmo is the complete opposite of Cosmo. Cosmo is kind, happy, caring, pleasant, thoughtful, and amazingly dumb, but Anti-Cosmo is extremely destructive, menacing, selfish, cruel, mean, evil, greedy, ruthless, sadistic, fiendish, truculent, diabolical, scurrilous, and manipulative, so he possesses a high-level intellect, and is a knowledgeable criminal mastermind. Anti-Cosmo is colored blue like all Anti-Fairies, has a monocle over one of his eyes which he can't see without, and wears a derby and a kind of coat or suit and, unlike Cosmo, speaks with a cultured British accent. He is married to Anti-Wanda, and Anti-Cosmo's castle is most likely not open to anyone except the Pixies, as seen in "Fairly Odd Baby". Since Cosmo used to be the last Fairy baby ever born, Anti-Cosmo may have been the last Anti-Fairy baby ever born until Anti-Wanda gave birth to their son Foop.
Anti-Cosmo has once switched Fagiggly Glands with Cosmo. But, unfortunately, it changed their voice too. As quoted by Wanda after Anti-Cosmo spoke in Cosmo's voice: "Bye Timmy, bye Wanda!".
- Anti-Cosmo calls Cosmo an "ignorant boob" many times in "The Gland Plan".
- Anti-Cosmo has appeared in "That Old Black Magic", "The Gland Plan", "Fairly Oddlympics", "Fairly Oddbaby", "The Jimmy Timmy Power Hour 2", "Anti-Poof" and "Balance of Flour".
- Although Anti-Cosmo is the opposite of Cosmo, he still loves his wife, Anti-Wanda.
- In "The Jimmy Timmy Power Hour 2", Anti-Cosmo's canine teeth are like those of sharks.
- Anti-Cosmo occasionally calls other characters "Clarice". This is a reference to the Hannibal Lecter movies.
- Anti-Cosmo is the complete opposite of Cosmo in terms of intelligence. Whereas Cosmo is considered a lovable idiot, Anti-Cosmo is a diabolical criminal mastermind.
- Like all Anti-Fairies, he has blue hair, shirt, and skin, black wand, wings, and is a villain.
- While Cosmo is often despised by his fellow Fairies due to his idiocy, Anti-Cosmo is well respected among his kind due to his intellect.
- Proof of this is that he often acts as the de facto leader of the Anti-Fairies rather than Anti-Jorgen.