The Rowdyruff Boys appeared as a cameo in the original Panty and Stocking Vs. The Powerpuff Girls, opposite Scanty and Kneesocks. Both groups were intent on rapping but were immediately removed by the Announcer to avoid overcrowding the battle and stretching material too thin. Only Brick actually spoke, and was voiced by Paul Bergen.
They appeared as proper rappers in Panty and Stocking Vs. The Powerpuff Girls: The Unshitty Version. This article is specifically about the cameo; for information on their later appearance, see Brick, Boomer and Butch.
Information on the cameo
The Rowdyruff Boys, Brick, Boomer and Butch, are antagonists in The Powerpuff Girls and evil, male counterparts to the titular trio created by the villainous ape Mojo Jojo from "snips, snails and puppy dog tails". They were killed by the girls in their first appearance by being kissed thus triggering an explosive reaction in them due to their fear of "cooties", but were revived years later by the demon HIM and made several appearances during the show's final season.
Yo, you call, Blossom?
Yeah, the boys are back in town!
Well, I love eating bugs-(Interrupted)
The original script only called for "Well I-"; "I love eating bugs" was improvised on the spot by Paul Bergen.