Chapter 11 - S2-E3
Trivia: The idea of "mental contamination" mentioned at the start of the episode is real, and the demonstration using cheerleaders is based on fact. 5 cheerleaders and 5 other students had seizures in a town in 2002, in 1952 165 cheerleaders fainted before half time at a football game. A famous incident was in Le Roy in 2011 - those who were featured in the press took longer to recover than those who didn't, suggesting a strong social/communication basis.
Trivia: The Time Demons bear a strong resemblance to the Blue Meanies from the Beatles' Yellow Submarine.