Two atoms walk into a bar. One says to the other, "I think I've lost an electron!" "Are you sure?" "Yes, I'm positive!"

A neutron walks into a bar and asks, "How much is a beer?" The bartender says, "For you, no charge."

The tachyon orders a beer. A tachyon walks into a bar.

Some helium floats into a bar. The bartender says, "Get out! We don't serve any noble gases in this bar." Helium doesn't react.

A neutrino walks into a bar. The bartender says, "Get out! We don't serve any neutrinos in this bar." The neutrino says, "Don't mind me; I'm just passing through."

A room temperature superconductor walks into a bar. The bartender says, "Get out! There are no superconductors allowed in this bar." The room temperature superconductor leaves without putting up any resistance.

Two bacteria walk into a bar. The bartender says, "Get out! We don't serve any bacteria in this bar. The two bacteria say, "Hey, but we work here. We're staff."

A parasite walks into a bar. The bartender says, "Get out! No parasite are welcome in this bar." The parasite says, "Well, you're not a very good host."

An infrared photon walks into a bar and says, "Is it hot in here, or is it just me?"

Schrodinger's cat walks into a bar... and doesn't.