In terms of kids' costumes, the ones that really bother me are ones that don't really disguise much of your body. I understand these aren't exactly Hollywood-quality costumes, but I still prefer it when you actually look kind of like what you're supposed to. I take particular issue with the costumes like this. Look, Big Bird has an extra head growing out of his neck! Yeah, I understand that putting a full-face mask on a little kid isn't recommended, but it seems like they could have put a little more effort into the outfit. And this is even worse. Poor Jigglypuff has a human child bursting out of his body.
For my part, I mostly wore animal costumes when I was young. I was a panda, a cat (which used the same body as the panda, but with a tail attached), an elephant, and a stegosaurus. I later used the elephant costume, with some alterations, to dress up as Kabumpo for two Oz Conventions. More recently, I've dressed as a knight, a pirate, and a doctor. I'm pretty sure I won't be dressing up this year, as it looks like I'll be working on Halloween night. Besides, there aren't really as many occasions for adults to be seen in Halloween costumes, unless you're the kind of person who gets invited to parties, which I most assuredly am not.