What's White and Black?

I walk into one of those 24 hour convenience stores. It's late at night and I seem to be alone in my need of convenience. I put a loaf of bread on the counter. The man behind waits patiently. Is that all? He asks. Yes, I reply, waiting for him to ring it up. Are you sure? He says, looking at my other hand. At that moment I remember I've come out with half a pack of penguins. Chocolate biscuit penguins that is, not swimming and fish eating penguins; that would be weird. Still, this could be difficult to explain. I brought these with me, I venture. You've brought your own penguins? He repeats, raising an eyebrow. I start to say I was hungry and trail off. When I think I look guilty, I start acting guilty. Suddenly I remember how I can prove it. They're refrigerated! I burst out. They're what? He replies. Do you refrigerate your penguins? I ask him. No, he says, why would we? They taste so much nicer, try one, I say, and just like that, to spare my ass from jail, I spill the beans on one of my most closely guarded secrets.