Seven. One to change it and the other six to sing about how good the old one was.
or
Only two, but the hard part is getting them into the light bulb.
or
Two, one to call Daddy, and one to get the (pick one:) mineral water/Tab.
or
I find you very attractive.
or
Because he was bald!
or
Two, one to call the electrician, and one to mix the drinks.
or