I'm not sure if this has been brought up on any of the Ernie and Bert threads before or not, but a great classic one is the Ten Q one! Ernie asks Bert to count to ten with him using the letter Q. Ernie starts with one Q. Then Bert says, "Two Q." And they continue until Bert says, "Ten Q." Then Ernie says, "What was that,Bert?" Bert again says, "Ten Q." Ernie says, "I still didn't hear you , Bert." Bert says, "Ten Q! Ten Q! Ten Q!" Ernie responds with, "You're welcome You're welcome You're welcome, Bert. Kee hee hee hee hee." I've used this gag on people from time to time ever since. But in the form of algebra instead of counting. Like I'll ask, "How much is 4c plus 4c?" Usually people don't recognize its algebra and thus don't even understand the question! After 2 or 3 more algebra questions like this they get the idea, and I then ask how much is 5 Q plus 5 Q and get the intended answer: "Ten Q!" Why, you're quite welcome.