Kris: The most common way is by naturally being an animagus, like Professor McGonagal. That's the simplest way, but it's much harder if you're not lucky enough to have that ability.
Kris: As I said, I mastered Transfiguration. So I have enough skill to change and shift my body as I see fit. I could even *Shifts and looks like a girl with bright red hair and freckles* be a girl, or an old man *Shifts and looks like Filch*
Jess: -Smirks- The filch look suits you. Just wondering, how long would it take to learn how to do stuff like that?