Two. One to change it and one to yell "Ta-daa!" when he's done.
One to put in the new one, and two to sing about how good the old one was.
None, they prefer to live in the dark.
None. Once the bulb goes out, they replace the house.
A: None. They have a machine that does that now.
Amadeus Vult!
Because he said Punch's line.
An acrobat.