He was voiced by Patrick Pinney.
Along with his fellow agents, Underville was involved in Benedict's plot to steal a tractor beam from a U.S. military base so that they can use it to move the Moon into creating a new Ice Age to raise test scores. Following the Legion's takeover of Third Street Elementary (as it was closed for summer vacation), Benedict assigned his agents to act as guards, and Underville was tasked as a lookout alongside Henderson, Smithson, Franklin, Morrisey, and Goodman in front of the school.
Following the capture of Principal Peter Prickly and T.J. Detweiller when they investigated of what's going on, T.J.'s friends decide to take action by gather all of the students and teachers to help reclaim the school and defeat Benedict. As part of the plan, Mikey stands behind and on top of a bush singing, diverting the attention of Underville and the other guards. Annoyed by this, Underville and the guards tried to get rid of Mikey, but they fall into a huge dug pit created by the Digger Twins using space shovels.
He was eventually arrested and sent to prison alongside Benedict and his other men after their plot was foiled.