Not exactly Quislings but you get the picture.

In Max Brook's novel World War Z, Quisling is used as a term to describe people who had, in effect, gone over the deep end. The psychological strain put on them from the Zombie hordes caused their minds to crack and a sort of emotional contagion occurred in which uninfected humans began acting, sounding, moving like and even believing they were the undead. Although unconvincing the actual zombies, normal human beings were often fooled by this emotional and psychological breakdown.