[Bear_in_RoseBear]

Did we ever see him change before the last book?

Not that I recall!

[TightyRighty]

I don’t recall either. I know there were a ton of references to him being bat-like. The vampire essay Lupin asked the kids to write in Azkaban leads me to believe he must have been unregistered and Lupin must have known. Instead of jumping on the Animagus(?) clue - everyone thought Snape was a vampire.