Proving that you can never go too far to make a pun work, my mom forwarded these gems:
A marine biologist developed a race of genetically engineered dolphins that could live forever if they were fed a steady diet of seagulls.
One day, his supply of the birds ran out so he had to go out and trap some more. On the way back, he spied two lions asleep on the road. Afraid to wake them, he gingerly stepped over them. Immediately, he was arrested and charged with transporting gulls across sedate lions for immortal porpoises.
There were three Indian squaws. One slept on a deer skin, one slept on an elk skin, and the third slept on a hippopotamus skin.
All three became pregnant, and the first two each had a baby boy. The one who slept on the hippopotamus skin had twin boys.
This goes to prove that the squaw of the hippopotamus is equal to the sons of the squaws of the other two hides.