In 'A Fairly Odd Movie: Grow Up, Timmy Turner!', Timmy Turner is a grown-up 23-year-old who is still living in Dimmsdale, but no longer has his fairy godparents Cosmo and Wanda. Timmy's life takes a drastic turn when he discovers that the rulebook which grants him his wishes has fallen into the wrong hands. With the help of his childhood friend Tootie and his former babysitter Vicky, Timmy must find a way to stop the evil book from destroying both the fairy world and the real world.

Timmy Turner, his fairy godparents Cosmo and Wanda, and his friend Tootie go on a summer vacation to Hawaii. They encounter a villain who tries to ruin their vacation and must chase him across the island. Along the way, Timmy discovers new love interests, encounters magic and surrealism, and confronts unexpected surprises.

In this live-action TV movie, Timmy Turner must navigate Santa's Rulebook and save Christmas with the help of his fairy godparents.