Take away his credit card
or
They screw millions of bulbs every day, but when it comes to your bulbs, there's no record.
or
Only one, but she/he'll have to go out and buy the light bulb adaptor card first, which is extra.
or
A snail because it carries it's home.
or
Two — one to change the bulb, and one to write a song about how good the old light bulb was.
or