Summary: Snape decides to learn his animagus form at the same time as Harry.
~The two have the same animagus form, with Snape being older than Harry
~include bits of their physical appearance that convert to their animagus form. (Like, Harry keeps his green eyes, Snape his crooked nose, etc.)
~Be reasonable with the emotions, no easily-loving Snape or super-submissive Harry
~Hedwig recognizes them and helps them.
~Harry is abused by the Dursleys, and Snape finds out
~They are trapped in their forms
~They TEMPORARILY lose their memory
~Animal instincts override human ones
~Snape adopts Harry