Three. One to change it while the other two argue about how old the old one is.
Because he might Pikachu!
Asparagus...
Fish
We may never know the truth.
Because of his enthusiasm for Carbon-Dating.
Someone whose career is in ruins.
The old one was made of steal.
Seven. One to install the bulb and six to figure out what to do with the old one for the next 10,000 years