Lobsters "
Homardware.
They were both two shellfish
Hand them a mechanical pencil with the lead out and see how the use it. Child A: look mom I'm a doctor! - expect them to live to 80+ years. Child B: look mom I'm a heroin user! - expect them to live to about 27.
Those who understand binary, those who don't, and those who weren't expecting a base 3 joke.