Transforming in general (was re: Hermione's Patronus)

[Rachel]

No: HPFGUIDX 124162


Jim, quoting from PoA:
> Later, Harry learns for sure, as Lupin is packing his bags:
>
> "Harry told Lupin what had happened. When he'd finished, Lupin 
> was smiling again...
> 
> Lupin again: "Yes, your father was always a stag when he 
> transformed," he said. 


I never really noticed it before, but when I was reading through this 
thread that line strike me as odd.  Why would Lupin need to say "was 
always"?  Is it possible for people to have more than one animagus?

Rachel (who wonders why this has never struck her as odd before).