Ah-choo-choo!
or
Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes.
or
One minds the train, one trains the mind.
or
Because sometimes you can get rid of cancer.
or
Twenty. One to hold the bulb, two to turn the ladder, and 17 to be on the guest list.
or
In the neigh-borhood.
or