Sorry. Someone had to do it.
1. A vulture boards an airplane, carrying two dead raccoons. The Stewardess looks at him and says, "I'm sorry, sir, only one carrion allowed per passenger."
2. Two fish swim into a concrete wall. The one turns to the other and says "Dam!"
3. Two Eskimos sitting in a kayak were chilly, so they lit a fire in the craft. Unsurprisingly it sank, proving once again that you can't have your kayak and heat it too.
4. Two hydrogen atoms meet. One says "I've lost my electron." The other says "Are you sure?" The first replies "Yes, I'm positive."