I personally think it's really easy to overlook the clown aspect of him and just see him as an awesome rainbow-coloured sheep. He may be a little creepy at first, but really, he's an awesome villager. I kind of regret not picking him up in the campsite.
I find clowns really creepy, but Pietro doesn't give me the clown feel. To me he is just a rainbow ball of cuteness. He was the first villager to move into my town and I won't let him leave now. He's such a sweetheart.
Pietro is hilarious. The idea of a rainbow clown sheep is so silly, but it works in the world of Animal Crossing. Plus, he's a smug villager, and I love smugs so much.