Tadpole grew up fast, in Minecraft you grow up fast. Unless you don't wish to. So when he turned 11, he became a recruit. Kermit and Jessica didn't want him to, but Sky managed to talk them into it.

Tadpole isn't a full recruit like Scarlet, Mith, or Mau, he can only fight in grounds. And since he is slight half frog, he makes sure no squids are in the lake or pools.