He is a black and white clown who was only featured in the episode, "Mime for a Change" and the villainous alter-ego of Rainbow the Clown who transformed into Mr. Mime after a freak accident with a bleach truck.
Mr. Mime's first appeared in the episode "Mime for a Change" when he sought to eliminate all color from Townsville, reducing it to black and white, which in turn drained the city of its vibrancy and happiness. He was eventually reverted back to his normal self by thePowerpuffGirls, but was still beaten up and sent to jail regardless. Rainbow was seen in the later episode "Birthday Bash" as an entertainer at the girls' birthday party, meaning that he had at least been released early and was on good terms with the girls. Yet his alter-ego, Mr. Mime, appeared in "Bought and Scold" and "Daylight Savings".
When questioned about Rainbow being sent to prison regardless of being cured on Twitter, series lead Craig McCracken responded "I think we just thought it was funny that the girls beat up the bad guy like they always did. I wouldn’t do this “joke” today."
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.
Mr. Mime is possibly named after the Pokémon of the same name, due to the fact that both Pokémon and The Powerpuff Girls were (and still are) popular at the time.
Mr. Mime resembles a black-and-white version of Koko the Clown, a Betty Boop character (from Fleischer Studios) deriving from the Golden Age of American animation.
He sounds like Dog from CatDog.
It could be argued the bleach damaged his brain and gave Rainbow dissociative identity disorder, making Mr. Mime an entirely different personality.
Season 1:Monkey See, Doggie Do • Mommy Fearest • Insect Inside • Powerpuff Bluff • Octi Evil • Geshundfight • Buttercrush • Fuzzy Logic • Boogie Frights • Abracadaver • Telephonies • Tough Love • Major Competition • Mr. Mojo's Rising • Paste Makes Waste • Ice Sore • Bubblevicious • The Bare Facts • Cat Man Do • Impeach Fuzz • Just Another Manic Mojo • Mime for a Change • The Rowdyruff Boys • Uh Oh Dynamo Season 2:Stuck Up, Up and Away • Schoolhouse Rocked • Collect Her • Supper Villain • Birthday Bash • Too Pooped to Puff • Beat Your Greens • Down n' Dirty • Dream Scheme • You Snooze You Lose • Slave the Day • Los Dos Mojos • A Very Special Blossom • Daylight Savings • Mo Job • Pet Feud • Imaginary Fiend • Cootie Gras • The Powerpuff Girls Best Rainy Day Adventure Ever • Just Desserts • Twisted Sister • Cover Up • Speed Demon • Mojo Jonesin • Something's a Ms. • Slumbering with the Enemy Season 3:Fallen Arches • The Mane Event • Town and Out • Child Fearing • Criss Cross Crisis • Bubblevision • Bought and Scold • Gettin' Twiggy With It • Cop Out • Three Girls and a Monster • Monkey See, Doggy Two • Jewel of the Aisle • Super Zeroes • Candy Is Dandy • Catastrophe • Hot Air Buffoon • Ploys R' Us • The Headsucker's Moxy • Equal Fights • Powerprof. • Moral Decay • Meet the Beat Alls • Helter Shelter • Power Lunch Season 4:Film Flam • All Chalked Up • Get Back Jojo • Him Diddle Riddle • Super Friends • Members Only • Nano of the North • Stray Bullet • Forced Kin • Knock It Off Season 5:Keen on Keane • Not So Awesome Blossom • Power-Noia • Monstra-City • Shut the Pup Up • Toast of the Town • Divide and Conquer • Burglar Alarmed • Shotgun Wedding • Save Mojo • Substitute Creature • The Boys Are Back in Town • See Me, Feel Me, Gnomey • Pee Pee G's • Boy Toys • Seed No Evil • The City of Clipsville • Lying Around the House • Bubble Boy • A Documentary • Girls Gone Mild • Curses • Bang for Your Buck • Silent Treatment • Sweet 'n' Sour Season 6:Prime Mates • Coupe D'Etat • Makes Zen to Me • Say Uncle • Reeking Havoc • Live & Let Dynamo • Mo' Linguish • Oops, I Did It Again • A Made Up Story • Little Miss Interprets • Night Mayor • Custody Battle • The City of Nutsville • Aspirations • That's Not My Baby • Simian Says • Sun Scream • The City of Frownsville • West in Pieces • Crazy Mixed Up Puffs • Mizzen in Action • Roughing It Up • What's the Big Idea? • Nuthin' Special • Neighbor Hood • I See a Funny Cartoon in Your Future • Octi-Gone Reboot: