I find snakes in hats hilarious. Mostly people just set tiny hats on their heads and take pictures while they sit still. No harm in it.
My Christmas/Yule photos were my little MBK sitting there staring at me after I put a bunch of (not sticky!) bows on top of him. He didn't care. :P
As to sweaters on dogs--some need them in the cold. See Greyhounds, for example. And...sometimes people are being silly, but well.