When I'm at my register, my life revolves around the phrases, "Hi, how are you doing? Could I have your zipcode, please?", "Your total is klshgkhdrgrld!", "Could you sign here, please?" and, "Have a great day!" After a while, though, I start to mix everything up. I'll ask for their zipcode for a second time while I'm handing them their receipt. And then I'll be all like, "Oh wait! Haha, I meant, could you sign here, please?" And they'll smile and nod, and then later, as they're packing up their cars, they'll tell their children that that's why you stay off drugs.
Also, every time now that I talk to someone I don't know or haven't seen in a while, I have the strange urge to cheerfully and plasticly wish them to have a great day. I guess it could be worse, though. I could be asking them for their zipcode.