Clancy, featured in the episode "Side Effects", is a blue-skinned man who has the ability to control any type of insect; the source of this ability is never explained. Clancy always speaks using first-person plural pronouns like "we", as he speaks for all of his insects as well as himself. He lives at 8610 Chester Street, an abandoned apartment building. When Councilwoman Liang tries to redevelop the area and have his home torn down, he kidnaps her with the intention of feeding her to his insects. Fourarms stops him, accidentally destroying his home in the process when Clancy's insects swarm him.

After that plan fails, Clancy tries to cause the nearby nuclear power plant to meltdown, killing everyone and everything in the city. Clancy makes himself a protective suit out of cockroaches (which are highly resistant to nuclear radiation) in order to survive the blast. A sick Heatblast whose powers are reversed by the virus, giving him the ability to control cold instead of heat, stops this plan. Finally, he attempts to take revenge on the trio. Once again, he is stopped, this time by Max's San Ju Yen Pien cold medicine , which attracts the bugs and overrides Clancy's control over them, at which point Max easily knocks him out.

Clancy doesn't appear to actually be deranged at first, just trying to save his home (although his comment about having his bugs eat the mayor seems a bit overboard), but starts doing things that show him to be sociopathic once it's destroyed along with many of his bugs.

In "Ben 10 vs. The Negative Ten (1)," he joins the Negative 10 and is now mutated into a bug-like state.