I've never done well with the 'serene' image of yoga. Serene isn't something that comes naturally to me; I do yoga to become more like that. Naturally, I am in equal parts anxious and silly. The happier I am, the sillier I get.
Which is not a bad thing, in my (cough) humble opinion. In same opinion, I think the yoga world has a slight tendency to take itself too seriously.
It's not necessary.
You can be plenty spiritual and still be happy/silly/have fun.
In fact, I'd be suspicious of someone who claims to be spiritual, but lacks a sense of humour. If you've ever seen the Dalai Lama speak (and nobody's going to argue about his spiritual cred) you will know that he's got a great sense of humour.
If you find someone taking themselves too seriously - or trying to get you to - you may need to call on a mmYoga Superhero to save the day...
Captain Sneaky (street name Karen Chow)