Neutrinos are a race of microscopic alien creatures. They invade the minds of other organisms to steal information for whoever hires them, leaving the victim's body in a vegetative state. They were given the nickname "Neutrinos" due to their microscopic size. Their real name is unknown.
The Neutrinos first appeared in Journey to the Center of Mikey's Mind where they were hired by Vrax Belebome to obtain information from Michelangelos Subconscious. With the help of the inner Michelangelo and the figments of the characters within Michelangelo, the Neutrinos were defeated.