At some point probably

Remus: Do you think that your Animagi animals say something about you?

James: Definitely! Sirius is energetic and loyal but he'll bite back if he feels threatened. That's why he's a dog!

Sirius: And James, you're like the king of the forest, wanting to look out for your friends and family.

Peter: So, why am I a rat?

Other three: ...

Sirius: I bet it's because you like cheese.

Other three: -Murmurs of agreement-