Three - one to cast the bulb into the outer darkness, and two to catch it when it falls.
or
It takes them a long time to swallow their pride.
or
It takes two. One to change the bulb, and the other to kick the switch.
or
What's the use, they'd still have bear feet
or
One has claws at the end of its paws and one has a pause at the end of its clause
or