Refractions
Refraction of sunlight in raindrops
Prism (Note: I made this joke up. Sorry if this little note refracts from the humour.)
Because he thinks they're part of the illumi-naughty
So they can see where they are going
Diving
One bursts into flames in the sunlight, and the other is a vampire.
Math-you.
They both have an alge-bra.
It was a clear day
Hue hue hue hue
A. Engineers.
The other says, "I'm a big metal fan"
Eventually the savings bond will mature and begin to earn money.
On your Marx, get set, go!
Shine a flashlight in their ear.
Light