i dont know k its old or new . . .but i really laughed . . .
A little girl was talking to her teacher about whales. The teacher said it was physically impossible for a whale to swallow a human because even though it was a very large mammal its throat was very small. The little girl stated that Jonah was swallowed by a whale. Irritated, the teacher reiterated that a whale could not swallow a human; it was physically impossible. The little girl said, "When I get to heaven I will ask Jonah". The teacher asked, "What if Jonah went to hell?" The little girl replied, "Then you ask him".
I heard its different version in which the discussion was between a christian priest and an agnost, where the agnost tries hard to convince the priest that the story about whale swallowing Prophet "John" (Hazrat Younis PBUH, I got that right??) can't be true because of above reason (throat!) and then the priest replies him back with that heaven and hell answer.
Either way its funny :).