But, actually, he chose a stag because it was large, powerful, and fast. It could survive a werewolf attack (assuming the worst case scenario happened). When the Marauders told Remus they were animagi.
Harry Potter Characters: In the Books vs In the Films. Some are spot on, some are a little off but still great <<— I agree! Also, they tried with Daniel and the coloured contacts but he was allergic to them so they decided against using them again.