well, it's easier to be funny when you're happy... (and it's easier to be happy when you're funny)
One way of being funny is just doing things other don't dare or want to do...
I mean (how I can explain this?
), lack of shame is funny... Like speaking about topics many people refrain to talk about (sex...) when they're thinking about that.
So sincerity can be funny, like saying what you really have in mind...
If you go to a karaoke and just sing to a Sinatra song, now that's not funny. But if you dare to impersonate Sinatra vocal things and gestures, that's funny... cause it shows you have no shame.
It's basically a "I do what I want to do, no matter what they think, so I'm free" thing... so there's a little celebration called laughter