Depends on the pet really.
I used to have two dogs that LOVED wearing clothes, it was ridiculous. They liked wearing sweaters and shirts all through winter and didn't mind coats if it was colder or costumes for short periods (or longer if the costumes were very basic). However after that, I had a cat who absolutely hated clothes. A hat or a festive collar was all she'd tolerate.
Right now we have two guinea pigs and a snake. I love those tube "sweaters" people make for snakes so I'd like to get one for Rose, I don't think she'd mind it for a short time. The boys I'm not so sure about. They might allow a very loose costume or hat, but we haven't tried anything yet. If they don't like it we wouldn't force it.