Talk about contradiction...

its probably that he wasnt to fire OP so hes looking for reasons and sowing discontent.
Sorry OP, its a common management trick. Even if its not, you might want to look into a new job, cause who wants to work in a place like that.

Some people are impossible to please

Well in all honesty, if someone was completely lacklustered and dull one week and suddenly started excessively laughing the following week, I would think that person is just being a smartass. Maybe that's what OP's boss felt.

It sounds as if he just wants to get rid of you. Time to seek another position.

that is not necessary true... some people are just annoying. But if you don't like your work place, maybe it's a good idea to seek for something else.

This sort of happened to me. I suffer from resting bitchy face so my manager told me I should try to smile more to make customers feel welcomed. Then she told me to stop because my forced smile "makes me look like a serial killer"

Just accept you will never be right and move on.

They can't exactly move on, not when it's their job ://

Man, no matter what you do, he will find an excuse. I suggest finding a new company to work with.

Your boss sounds like a huge dick, I'd just ignore what he says about laughing and smiling

Damned if you do, damned if you don't.

I was going to say that maaaannn!

Maybe you should consider laughing so much you'll put the Laughter in Manslaughter when you're wrecking your bosses face in for being such a prick.

reprimand him for being a douche!

Sounds like your boss has a bad case of "I don't like this person so I'm going to find reasons to get this person fired because I'm a miserable prick."