Bart: [walking up to a crowd of striking teachers] Now for Operation Strike-Make-Go-Longer.
[speaking to teacher] You know, I heard Skinner say the teachers will crack any minute.
The teachers whisper it forward through the line.
Teacher: [speaking to Edna] "Skinner said the teachers will crack any minute, purple monkey dishwasher."
Edna Krabappel: "Well! We'll show him, especially for that 'purple monkey dishwasher' remark!"
This is most likely a reference to Chinese whispers, where a story or phrase passed sequentially from one member of a group to another is often grossly distorted once it reaches the intended recipient. The remark itself has achieved a notable amount of pop culture recognition as an inside joke between Simpsons fans. A Purple Monkey Dishwasher zine (Modbury North, S.A. : Purple Monkey Dishwasher, 1996-1999) was even published for a short time.
I see a lot of this going on in these forums!
