Drinking, bathing, washing, swimming, etc.
or
Billllyuns and billllyuns. Light bulbs are part of the interstellar "goo" that pervades our universe; they are star stuff.
or
Because they don't fit on a ironing board
or
Twenty. One to hold the bulb, two to turn the ladder, and 17 to be on the guest list.
or
I just found the Bush that Jeb lost."
or