Worms.

[Keith Dean]

A little boy and his grandpa were sitting in the garden when
the little boy said, "Grandpa, grandpa, see that little worm
over there. I bet I can put him back into his hole."
Grandpa accepted the bet and they agreed on £5.
"You'll never be able to do it, lad, the worm is too limp to be
pushed back."
The little boy disappeared inside and came back with a can
of hairspray. He sprayed it all over the worm until it became
as stiff as a board and then quite easily stuck it back in the
hole.
"See, Grandpa, I win my bet."
Grandpa handed over £5 and said, "I'm just popping into
the house, I'll be with you in a little while."
Sure enough, 10 minutes later he reappeared and handed
the boy another £5.
"But Grandpa, you've already paid me," said the boy.
"Ah yes," smiled Grandpa, "but this is from your Grandma."