In South Park, S01 E03 Weight Gain 4000 starts with the conversation between the boys in a classs room and Cartman thinks something else instead of rainbows.
Kyle: Nobody hates rainbows.
Stan: Yeah, what's there to hate about rainbows?
Cartman: Well, you know, you'll just be sitting there, minding your own business, and they'll come, marching in and crawl up your leg and start biting the inside of your a**, and you'll be all like: "EHY! GET OUT OF MY A** YOU STUPID RAINBOWS!"
Stan: Cartman, what the hell are you talking about?
Cartman: I'm talking about rainbows, I hate those friggin' things!
Kyle: Rainbows are those little arches of color that show up during a rainstorm.
Cartman: Ohh, rainbows. Oh yeah, I like those, those are cool.
Stan: What were you talking about?
Cartman: Huh? Oh, nothing, forget it.
What was Cartman thinking about before Kyle said they actually are? I think he was meaning some insects but no insect's name is no where near to rainbows. Is it known which insect or what he was thinking about?