[This one works best when spoken aloud.] http://www.xue90.cn来自《幽默学英语》网
Once upon a time a mother skunk had two children named "In" and "Out". They were very active children and whenever In was in, Out was out. When Out was in, In was out.
One day when Out was in and In was out, the mother skunk said "Out, go out and find In and tell In to come in." Out went out to find In to bring In back in. Within a minute, Out came back in from going out and Out brought In right back in.
Amazed, the mother skunk said, "Out, you just went out to find In and brought In right back in! How did you do it?"
To this, Out replied "Instinct!" [In stinked]