http://www.rinkworks.com/said/kidscience.shtml

 

My favourite: "When they broke open molecules, they found they were only stuffed with atoms. But when they broke open atoms, they found them stuffed with explosions."

Hehehe...I couldn't decide on one, but these three had me in some pain:

 

"One horsepower is the amount of energy it takes to drag a horse 500 feet in one second."

 

"Water vapor gets together in a cloud. When it is big enough to be called a drop, it does."

 

"A hurricane is a breeze of a bigly size."

 

My ribs hurt!

 

I once marked an essay that contained the phrase: "Ivan Pavlov, the father of salivating dogs..."