a neutron walks into a bar and order a beer.
he asks the bartender how much it costs
the bartender answers: for you, no charge

the neutron asked the proton
bartender: "are you sure?" and the
proton answered:"I'm positive!".
...

a garlic cheese sandwich walks into a bar.
he asks the bartender for a cola.
the bartender told him: "sorry, sir,
but we don't serve food here".