Sirius shrugged. "I don't know if I ever told you about when I got back. I was in Stubby's body all the time. After my first animagus transformation, I sometimes came back as him and sometimes as myself. And I'd often turn into the dog in my sleep. Slowly, that went away, and within I few months, I was always myself when I changed into a man. Then, a couple of weeks ago, I started turning into a dog in my sleep again, and twice I've ended up as Stubby when I tried to turn back." He grimaced.
"I'm actually wondering if I have some sort of sickness that's doing something to my magic -- you know, like leopard fever does? Occasionally, I just can't cast some normal charm, and then the next time, it's fine."