Parachute
There are five people on a plane: two pilots (they are married), Bill Clinton, his wife, and a boy scout. Suddenly one of the pilots shouts out, "We are running out of fuel!" Then the other pilot points to the four parachutes in the back and says, "Since there are only four, everyone will have to give reasons why they need to take a parachute."
The female pilot jumps up and says, "Well I'm expecting a baby!" So she grabs a parachute and jumps out of the plane. Then the male pilot jumps up and says, "That baby's going to need a father." So he grabs a parachute and jumps.
After that Bill Clinton jumps up, grabs a parachute and says, "Well the U.S. needs a president." No one objects, so he jumps off with a parachute.
Finally, there is only Mrs. Clinton and the boy scout. The boyscout says "Well, Ma'am, the President needs his first lady, so I guess you should use that last parachute."
"Don't be silly, son," she says handing him a parachute, "he grabbed your backpack! Let's go!!"