Peter Pettigrew was a man who had transformed into a rat. Ron Weasley ended up adopting said rat as a pet, naming him Scabbers.

Actually, the rat belonged to one of Ron's brothers before it was Ron's. He didn't adopt it.

Well, it was his during the books and the movies, so it counts.

It is his rat yes. I'm just saying, it was his brothers rat first, and so the brother named him Scabbers.

Ah. I had completely forgotten that little detail.
It's been....wow....it's been almost 10 years since I read the first book.

Tada.

still don't get it

Well, the Marauder's Map is sort of like a magical GPS, that shows everyone's name inside Hogwarts, as well as where they are. So, it would have shown both Peter Pettigrew's and Ronald Weasley's names inside the Gryffindor dorms together.

ohhhhhhhhhh
so Snape was implying that Ronald had a gay moment and no one questioned that... I see now