Twenty. One to hold the bulb, two to turn the ladder, and seventeen on the guest list.
or
Clerk: "Yes, sir. What size does your alligator wear?"
or
Only one, but she/he'll have to go out and buy the light bulb adaptor card first, which is extra.
or
Because they had so many knights.
or
Abominable! [A Bomb In a Bull]
or