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-