A male crab met a female crab at a party and asked her to marry him.  She noticed that he was walking straight instead of sideways.  Wow, she thought, this crab is really special.  I can't let him get away.  So they got married immediately.

The next day she noticed her new husband walking sideways like all the other crabs, and got upset.  "What happened?" she asked.  "You used to walk straight before we were married."

"Oh, honey," he replied, "I can't drink that much every day."