Maryann is a child Timmy encountered while exploring Cosmo and Wanda's fishbowl castle. After taking Cosmo's wand, he wishes her and two other kids out of their portraits hung in what he believes to be Cosmo and Wanda's "Hall of Fame". He, however, quickly finds out he misread the sign outside of the room. It turns out they were in the "Hall of Infamy", the worst of Cosmo and Wanda's godchildren.
He's tricked into giving the wand to Maryann, who reveals she wants to enact revenge on Cosmo and Wanda with it. After a scuffle with the other "Hall of Infamy" kids, she leads Timmy (and then Cosmo) in a chase to get Wanda's wand. She's able to get a hold of it but is thwarted by Wanda at the last second and put back in her painting.
It's also revealed by Wanda why she lost her fairies and ended up in the "Hall of Infamy". On the 28th of June 1914, she wished that Franz Ferdinand (Archduke of the Austro-Hungarian Empire) would be assassinated in Sarajevo, thus plunging the world into the First World War.
Description[]
Because she was wished out of a gray-scale painting, she is fully gray-scale herself, instead of the natural colors she had when she was alive. She wears a small dress and black Mary Jane shoes, and has ringlets and a bow.
Trivia[]
It is unknown how she could wish that the Archduke would be killed, because it states in Da Rules that a godchild cannot wish someone dead. It's possible this rule was created because of her. Maryann is also shown to be very manipulative (She was able to trick Timmy into giving her Cosmo's wand), so it's possible she could've found some sort of loophole.
Potential ways she could have wished someone killed:
It is possible that she got a Magic Muffin, making it possible for her to wish Archduke Ferdinand murdered without breaking Da Rules.
It is also possible that this wish was a secret wish, and that she wished that Wanda or Cosmo forgot about it like Timmy did in "Timmy's Secret Wish!". However, if this is the case, then it was most likely possible that she wished for something that caused Archduke Ferdinand's death instead of directly wishing it. Using magic direcly to kill someone is impossible as it will turn them into something else, which is made evident in specials "When Nerds Collide" and "Abra-Catastrophe!".
A third possibility is that she wished for You Doo Dolls for soldiers into assassinating Archduke Ferdinand (in this case, Gavrilo Princip, the Archduke's killer).
Another possibility is that she likely wished for a weapon and gave it to Gavrilo Princip, that he used to kill Archduke Ferdinand.