The snake jokes
Version 1: The national park version
A man camped in a national park, and noticed Mr. Snake and Mrs. Snake slithering by. "Where are all the little snakes?" he asked. Mr. Snake replied, "We are adders, so we cannot multiply."
The following year, the man returned to the same camping spot. This time there were a whole batch of little snakes. "I thought you said you could not multiply," he said to Mr. Snake. "Well, the park ranger came by and built a log table, so now we can multiply by adding!"
Version 2: The Biblical version
The ark lands after the Flood. Noah lets all the animals out, saying, "Go and multiply."
Several months pass. Noah decides to check up on the animals. All are doing fine except a pair of snakes. "What's the problem?" asks Noah.
"Cut down some trees and let us live there," say the snakes.
Noah follows their advice. Several more weeks pass. Noah checks on the snakes again. Lots of little snakes crawl over the earth, and everybody is happy. Perplexed, Noah asks, "Want to tell me how the trees helped?"
"Certainly," say the snakes. "We're adders, and we need logs to multiply."