Lenght of story and the posible time when it happend.
I mean, how long would his kits live?
Most glaring, if you go by the books.
And when Sirius died, four rather more intelligent than usual mutts lived on.
It says that it happend either a long time ago or last year.
But this one seems to speak against that.
And when Harry’s family went to pick out a dog fourteen years later, things came full circle, as Harry went home with Padfoot’s great-great-grandchild.
Besides, if this collie has deverted Serius from traking down Pettigrew after James and Lilly Potter where killed, wouldn't this mean that Serius wouldn't end up in Azkaban?
What are the dates, and which dog show/movie/cartoon have you crossed this with?
Lassie, Scoobi-do, ect?
The idea is good, but might I suggest another time aswell?
The time after Serius broke out of Azkaban and before he came to Hogwarts.
If it happens once......
Anyway, nice try.
Just needs a little more meat.