Dr. Rainbow the Clown is a clown who entertains children at parties. After a truck with bleach hits him, he turns black and white and gets superpowers. Rainbow's evil alter ego, Mr. Mime, has the power to erase colors by touch and even render objects and animals, people, and music mute. For instance at first, he touches the bleach trucker and secondly the little boy who holds a balloon. He turned back into a very grateful Rainbow after the girls perform a song that restores Townsville's colors. He thanks the girls for bringing him back to life, but they beat him up and send him to prison anyway. He is seen in later episodes such as Birthday Bash, still happy and cheerful as ever, suggesting that he was promptly released from prison and all has been forgiven, even was invited to The Powerpuff Girls' birthday party as a guest that The Powerpuff Girls eventually forgave him after the event of Mime for a Change. Rainbow was voiced by Tom Kenny.
- Mime for a Change (first appearance)
- Birthday Bash (as Rainbow the Clown)
- Daylight Savings (cameo) (as Mr. Mime)
- The Powerpuff Girls Rule! (cameo) (as Rainbow the Clown)
- Rainbow's alter ego, "Mr. Mime", shares the same name with a Pokémon.
- Craig McCracken actually wanted Rainbow to be forgiven for what he did as Mr. Mime, but Cartoon Network executives instead ordered he be arrested instead. But he returned in Birthday Bash as guest at The Powerpuff Girls's birthday party that he was forgiven by everybody in Townsville, including by The Powerpuff Girls because it wasn’t rainbow’s fault that he transformed.
- Mr. Mime resembles a black-and-white version of Koko the Clown, a cartoon character (from Fleischer Studios) deriving from the Golden Age of American animation.
- Mr. Mime's name pretty much based on Mr. Hyde from "Dr. Jekyll and Mr. Hyde" who is the evil alter ego of the good scientist, Dr. Jekyll. Rainbow becomes an evil black-and-white mime who hates colors and turns everybody and everything black-and-white-and-gray and mute every time he got bleached, which it also changes his personality as well.
- He sounds like Dog from CatDog.