The Troublesome Treachery of the Thieving Toot Fairy is the thirteenth episode of The Epic Tales of Captain Underpants and the final episode of season one.
It's a race against time as George and Harold try to get Mr. Krupp fired before he can have them expelled, and they have the help of the reluctant Melvin Sneedly, and another problem; they have to get past the security compound's walls and defeat the revenge-crazed Smartsy Fartsy (disguised as the Toot Fairy to collect the farts he needs to make an army for his revenge).
- It is revealed that Vil Endenemys is actually Melvin from the future.
- Melvin and his future self become the new principals and Krupp is fired.
- George and Harold get expelled.
- Moral: Revenge doesn't solve anything and makes you no better than your enemies.
- This is the first episode featuring Melvinborg. This is his only Season One appearance.
- Mr. Krupp suddenly loses his real hair when he worries himself getting fired from being principal.
- When Captain Underpants turns back into Mr. Krupp, he freaks out realizing he's naked, then he runs in his house leaving his cape outside on the ground, but when Harold and George spy on him from the tree through his window with him looking at the picture of him at school, he's suddenly wearing his cape again.
- Vil Endenemys only has one L, where did the one for Melvin Sneedly come from?