When kids grow up, fairies are assigned to new kids who need them. It's all about maintaining the Fairy Council's rules. Like, seriously strict stuff. So Timmy would lose them but another lucky kiddo would get Cosmo and Wanda.

They just leave, if I remember right, and Timmy wouldn't remember them anymore. But sometimes the show bends the rules for plot convenience, so who knows! 😂

Timmy grows up and Cosmo & Wanda go to Vegas. They gamble away all their magic. Duh.

Man, I remember seeing that in an episode where Timmy almost lost them because he grew too old or was too close to revealing them. It's like a clean slate for both parties. Really bittersweet.

They probably hang out at the Fairy Unemployment Office waiting for the next kid who can’t handle life and needs fairy intervention. JK, they move on to another kid.

Here's the deal: according to the Fairy Rulebook, which is a critical aspect of the show, when a child no longer needs fairy godparents, or if they reveal the existence of their fairies, they lose their fairies and their memories of them. The fairies get reassigned to another child in need of their help. This maintains the magical balance and keeps everything secret, but yeah, it's kinda bittersweet. Timmy would likely grow up without remembering most of his adventures.

So in the show, when kids grow up and don't need fairies anymore, the fairies' memories are wiped clean of that kid and they move on to another kid. Bummer for Timmy but that's how the fairy rules work!

They actually leave and go to a new kid! Sort of sad but also their job. I bet they get cool new kids to help though!