This was sent to the Gaggles of Groaners listserv by Bill Purcell. We both remember it from at least back to the 60s. “Himie Koshevoy’s Treasure Jest of Best Puns”, 1969, has a version of this story.

A family of skunks lived together, happily looking after each other. The two children, named In and Out, were especially close ( as these names often are).

One day they played Hide and Seek into the evening. At dusk the mother called them to dinner, but only Out came in.

“Where is your brother In, Out?” asked the father skunk, sitting down to the dinner table.

“I thought he came in ahead of me,” said Out.

“Well he didn’t, so go out and find In before you find yourself in serious trouble!” warned the impatient father.

It was now quite dark, but after searching for only a few minutes, Out found In and told him he’d better be getting inside quickly or they’d both be out of luck.

On seeing her two darlings returned to the family bosom so soon, the mother gushed, “Oh Out, how clever you are! How did you find your brother in the dark so quickly?”

“Not so difficult, Mother dear. Instinct.”