Well it’s a common consensus that he was a Goat animagus and he used to mess around with his brother, who were both goat farmers when they were younger.

How many registered Animagus are there in Harry Potter?

Animagus. These five people were wizards or witches (or both) who were known to be registered Animagi; however their animal forms are unknown. Hermione Granger referred to them by saying that there were only seven registered Animagi in the 20th century.

Was Lupin a registered Animagus?

Lupin isn’t at all an Animagus, but a pure werewolf (ie, a human being who shapeshifts into a wolf upon the full moon’s complete rising).