Three tortoises, Mick, Alan and Les, decide to go on a picnic. Mick packs a picnic basket with beer and sandwiches. The trouble is the picnic site is ten miles away, so it takes them ten days to get there.
When they get there Mick unpacks the food and beer.
"Okay Les, give me the bottle opener," Les says.
Mick gets worried. He turns to Alan, "Did you bring the bottle opener?"
Naturally Alan didn't bring it. So, they're stuck ten miles from home without a bottle opener. Mick and Alan beg Les to go back for it, but he refuses, as he says they will eat all the sandwiches.
After two hours, and after they have sworn on their tortoise lives that they will not eat the sandwiches, he finally agrees. So, Les sets off down the road at a steady pace.
Twenty days pass and he still isn't back and Mick and Alan are starving. But, a promise is a promise.
Another five days pass and he still isn't back. But, a promise is a promise.
Finally, they can't take it any longer so they take out a sandwich each and just as they are about to eat it, Les pops out from behind a rock and shouts...
"I KNEW IT!!! I'M NOT FUCKING GOING!"