Cheerios
A seven year old boy and his four year old brother are upstairs in their bedroom. The seven year old is explaining how he thinks they are old enough, now, that the two of them ought to begin using cuss words. When his little brother responds enthusiastically, the seven year old proposes the plan:
"When we go downstairs for breakfast this morning, I'll use the word "HELL", and you can say "ASS."
The four year old happily agrees to this great idea.
As the two boys are seating themselves at the breakfast table, their Mother walks in and asks her older son what he would like to eat for breakfast. The seven year old replies suavely,
"Ah hell, Mom, I'll just have some Cheerios."
"WHACK!" The surprised mother reacts swiftly. The seven year old runs upstairs, crying and rubbing his behind. With the clear tone of warning in her voice, the mother then asks the younger son most pointedly, "And exactly what did you think YOU would like for breakfast, young man?"
"I don't know," the four year old sobs, "but you can bet your ass it's not gonna be Cheerios!"