Brother and sister Marty and Mitzie are two of a kind. Already victims of Vicky’s ‘babysitting’, getting caught up in Timmy’s Fairly Odd Summer can only be an improvement for these two. They’re good kids that are no strangers to getting in trouble, but this time they’ll need to help out Timmy and his fairies on this summer adventure!
They were supposed to go on vacation in Hawaii with their parents, however, due to being busy, the parents hired Vicky to babysit them instead, much to their disappointment, as Vicky is still as mean as she always was.
By the end of the film, Cosmo and Wanda are assigned to them, as Timmy no longer needs them due to becoming a fairy himself.
Trivia
Marty and Mitzie are similar to Tammy and Tommy Turner, being a pair of siblings who get Cosmo and Wanda in the future and proposed end of the series.