Mama Cosma is Cosmo's overprotective mother and wife of Papa Cosmo who does not approve of Wanda marrying Cosmo. She has attempted and performed schemes to break them up but has always been thwarted by Timmy and Wanda.
When she is first introduced on the show, Mama Cosma is a sort of villain to Wanda and Cosmo's relationship. After an argument between them causes Cosmo to leave Wanda and return home to his mother, she attempts to hook him up with two prettier looking fairies, Star and Twinkle, but they are really just robots programmed to do whatever Mama Cosma says. Although she reveals at the end of the episode she has nothing personal against Wanda, later appearances seem to contradict this. She then gets chased by Cupid who was affected by a Love Arrow. She then warns Timmy, Cosmo, and Wanda that she will be back to end their relationship.
Another scheme that she attempted to pull off unsuccessfully is when she showed an audience of five hundred fairies an embarrassing tape about Cosmo's life, but she was thwarted yet again by Wanda and Timmy. Ironically, she was so moved at how much joy Cosmo brought to Timmy (at Wanda's expense) that she was among the 499 voters to vote for Cosmo to stay with Timmy and Wanda. The only person that actually voted for Cosmo to live with Mama Cosma was Cosmo himself as he assumed pressing the go home button would actually bring him home.
Since the birth of her grandson, Poof, Mama Cosma has become less hostile toward Wanda and no longer attempts schemes to drive her and Cosmo apart. Wanda also seems to be nicer to Mama Cosma, although she still tends to show a hint of animosity toward her, usually by making Wanda out to be a bad and irresponsible mother and criticizing Wanda's care of her grandson, Poof.
Mama Cosma is an extremely overbearing and protective mother. She kept a close eye on Cosmo until one day he left to "go get milk" and never returned, having left to marry Wanda instead. Apparently, she has nothing against Wanda, but dislikes anyone who tries to take Cosmo away from her. Mama Cosma is also Poof's only known grandmother. Mama Cosma was married to Papa Cosmo, whom she had her son Cosmo with, but when Cosmo was a baby he turned his father into a fly who flew off and was never seen again. Her husband's fate and her marital status is left unclear as of yet.
Mama Cosma is seen wearing a teal dress, with matching hair and eye color. Her hair is a sort of beehive type hair cut with many curls, it also looks like the same hairstyle, Marge Simpson has. Like most fairies, she has wings, a crown, and uses a wand to grant wishes. Mama Cosma is also presumed to be older than most other fairies on the show, as she appears to be physically older.