Just wondering

[ebragg31 at rochester.rr.com]

No: HPFGUIDX 12934

Okay, We know that when a person conjures up a Patronus,it takes on a 
differnet form for each person. I was wonderin do you think it would 
be the same for animagi?
Does the animagi pick which form they take or is it already 
predetermined?
When James, Sirus and Peter would change shape to help Lupin, I can 
see why a dog, but a stag and a rat?
Just a thought.