It takes two. One to change the bulb, and the other to kick the switch.
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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. . . .)
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Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes (knowing that it's already burned out).
or