They crack jokes.
Barium, Cobalt and Nitrogen.
It's all out of eggs.
Because the egg cracked a yolk.
They both like to crack open a cold one.
Sure, you know how it works, but now it's dead.
Both are a play on words.
The Circuits! (this is a joke i made up when i was like 10, i don't think it ever caught on)
Play hide and shell.