this one always cracked me and a co-worker up 17 years ago.

Buttered Cat Array:

When a cat is dropped, it always lands on its feet. And when toast is dropped, it always lands with the buttered side facing down. I propose to strap buttered toast to the back of a cat; the two will hover, spinning inches above the ground. With a giant buttered cat array, a high-speed monorail could easily link New York with Chicago.