Chickenpox

S2, E10: Cartman's mother plots to give the boys the chickenpox by sending them over to Kenny's for a sleepover. Both Stan and Cartman breakout but Kyle remains immune. Kyle discovers the parental conspiracy and with the other boys hires a prostitute to give their parents herpes. Meanwhile Kenny's mother and Kyle's mother reunite their husbands who were both childhood friends that drifted apart.