Anticlimax

Anticlimax: A sudden drop form the dignified or important in thought or expression to the commonplace or trivial, often for humorous effect.

Example:
"Hey, Big Shot," he teased.
"Hi, Reggie."
"Are you scared?"
"Alittle."
"Are you sure you want to do this?" he asked." I don't think it's a very good idea."
"Why?"
"White folks."
"Huh?"
"You'll stick out like a raisin in a bowl of rice."
Sylvia smiled at the thought, then looked fown at her shoes. "I know," she said with a sight.
(Fire from the Rock, Sharon M. Draper, Pg. 69)

This is an example of anticlimax because the boy Reggie, is trying to make a humorous quote to forget about the real situation. He does not feel like Sylvia going to an integrated school is a good idea. He feels like she's going to get hurt from all the white kids.