Seven. One to install the new bulb and six to figure out what to do with the old one for the next 10,000 years.
or
One's a spineless, poisonous blob. The other is a form of sea life.
or
One is a blood-sucking parasite, the other is an insect.
or
The guardians of the galaxy!
or
A snail because it carries it's home.
or