The ordeal of fruit

Two men shipwrecked on an island are captured by cannibals.
The tribal chief informs them the only way to avoid becoming dinner is to undergo the "Ordeal of fruit".
The two guys accept at once and the chief tells them to go into the jungle and collect 100 pieces of fruit and bring them back to him.
The first man comes back with 100 grapes. The chief says, "If you can shove all those grapes up your ass without laughing you will be released from the island." But no sooner than the first grape has reached his butt he bursts out laughing..... "Whats so funny?" the chief asks,"Don't you know we will kill you now!" "I'm sorry", the man says. "It's just that my friend is collecting bananas!"

pineapples would be better.

When I first heard this one (back when the crust of the earth was still warm), it was watermelons.