One in 3,000,000 has a chance of becoming a human being.
or
Because the chicken was on vacation.
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
Only one, but she/he'll have to go out and buy the light bulb adaptor card first, which is extra.
or