A camper is a person who sleeps outdoors.

Happy camper.

Does this have to do with someone who enjoys being in the woods?

You have a big smile on your face.

Why are you such a happy camper?

You know that audition I had?

Well, I just found out that I will be the new lead singer for the flaming frying pans.

Get out!

Congratulations.

I guess I'd be a happy camper too.

Ah, happy camper is a person who is cheerful or pleased.

Ah, person does not have to enjoy camping to be a happy camper.

By the way, this phrase can also be used to point out when someone is in a bad mood.

In that case, you say you are not a happy camper and that's English in a minute.