This is it

doo-wop... Actually, it's an excellent example of why I hate people, and the power of priceless comeback. God bless those who are quick with the wit.

Overly cheerful people just piss me off. I've got the same feelings towards them as I do those who are militantly religious - I'm happy for you, but keep it to yourself.

My standard response when grumpy to in(or overly)sincere "Have a nice day!"?

Thanks, I have other plans.