Five: One to change the bulb and four to pull the ladder out from under him/her.
or
She couldn't control her pupils.
or
Only two, but the hard part is getting them into the light bulb.
or
They screw millions of bulbs every day, but when it comes to your bulbs, there's no record.
or
I'll meet you at the corner.
or
Because it goes good with chips.
or