The Misfired Animagus

A misfired killing curse hit an animagus potion right behind Harry. The potion flask shattered, and Harry was helpless as it splattered onto his form. He then screamed, feeling his insides getting rearranged and his body forcefully shrinking. He feels a jerk scarily familiar to a port key. He blacks out. He wakes up in a field of grass. He freaks out when he realizes he has paws.