Bert was resting his hand on his table, and staring into space, until Ernie walked by.
"Hey, Bert. Wanna hear a knock-knock joke?" asked Ernie.
"Sure. What joke do you have in mind?" said Bert.
"I'll tell you." said Ernie, beginning. "Knock-knock."
"Who's there?" asked Bert.
"Rubber!" said Ernie.
"Rubber who?" asked Bert again.
"Rubber Duckie!" replied Ernie, holding out a Rubber Duck in his hand.
"I don't get it." said Bert, who didn't get the joke.
"Well, you should." said Ernie, laughing. "Everybody should get a Rubber Duckie, like me!"
"Not everybody." said Bert, who was unamused at Ernie's knock-knock joke.