S1·E31 Lice

When at skool one day, a child comes into class late because his head was itchy, which Ms. Bitters recognizes that it was due to lice. Before she can do anything, however, the lice infect the rest of the students in the class, so Ms, Bitters informs the Delouser, who proclaims martial law and the children are taken into separate rooms. However, Zim shows no sign of being infected by the lice, which causes the Delouser to take special interest in him.