Two: One to screw you out of a fee, and the other to send you to a store where they ran out of bulbs weeks ago.
or
They are triplets.
or
Because he want to wake up some day as America's First Dictator.
or
Can I have your hand, hand, hand, hand, hand, hand, hand, hand in marriage?
or
The question is irrelevant, since you couldn't find the dolls even if you knew how many. (Note: Well, this was a good joke in 1983-84. . . .)
or