Kappa

"Kappa? Cappuccino? Nah, makes me hyper."

Kappa (河童) are a species of demon in Japanese folklore. Due to the similarity in appearance, the Turtles are often confused for kappa, in a running gag that spans multiple universes. Like most demonic entities in Japanese myths, they are not evil by nature. Some are evil, some are simply mischievous, and others are even helpful.