"Well," Q says thoughtfully. "I did fairly well in Transfiguration. I know it's more complex than turning a pillow into a piano but the theory is basically the same. That's one of the things I wanted to ask you about. There isn't exactly a list of criteria for being an Animagi."
"That's another thing," Q leans forward. "How do you know? It all seems rather vague. Sort of like looking for your animal spirit guide." He clears his throat. "Severus says you're form is a, well, a Grim. Was that your choice or does it come about in some other manner. I mean, if I'm going to be a slug or a rhino or something, I'll take a pass."
"It wasn't you," Q says soberly. "And difficult as it may be, I'll do my best to remember that." He smiles. "I expect you'll remind me if I forget."
Q moves the books aside to make room for the coffee. He idly flips through one while Sirius fixes his coffee.
I guess he'd have to be or go stark raving looney-tunes!