Okay I have a cat that acts like a dog so I have the question of asking was my cat a dog in her past life or did a witch edit the dogs genetics while she was dying. My basic description of my cat I got her then blessed her with some magic charms and magic herself.
The simplest answer is probably the correct one: we humans make up all these stereotypes about species, and they're not always true. My uncle managed to train his cat not to jump on the table. I read (one of Malcolm Gladwell's essays, I think) that the most vicious dog attack was actually done by a golden retriever, a breed famous for being friendly.
It's a lot more plausible that your cat is just being itself and a lot less plausible that your cat honestly is acting like a dog due to magical or other influences. I met a cat that would climb into the shower with people and I have a dog that acts more like a cat. Those are due to their breeds, training, and circumstance, not due to anyone messing with or changing them.