The Amoeba Boys are a group of amoebas brought to life by the black Chemical Z rays. Their members are Silk Hat, Poncho, and Lady (also known as Violet), who is actually a female.
- Silk Hat is a blue amoeba that wears a top hat and carries a pipe in his mouth. He is the leader of the group.
- Poncho is a green amoeba that wears a cowboy hat.
- Lady (also known as Violet) is a pink amoeba that wears a pink sun hat. She is the only female member.
They are first seen in "The Infamous Amoeba Boys," where there is a flashback shown at the beginning of the episode where they are still water, but been hit by the black aura and become monsters. Weeks later, Poochi detected an aura of them and called the Powerpuff Girls for help. The Powerpuff Girls were searched for the group until they got tired while the Amoeba boys were in the bank waiting for there turn to be called. They missed their number and meanwhile a kid is making fun of them. And Lady is angry at the child. The guard saw them ramping a bank so he decided to kick them out. The girls told them to return to normal by sending them to Professor but Silk Hat told them, you can't catch a big villain, and so they complain to each other. They heard a dog voice and they have been returned to normal. And that day, they are not been caught by those girls instead of hiding in the underground.
Their weakness is the pink dog named Koyuki-chan (in Japanese).
The Amoeba Boys can combine with each other (becoming very large), but no superpowers to attack; however, they can only jump up and down. However, their sheer size is enough to make them dangerous when combined.