Originally, if this wasn't a special mini comic, I would have the Doctor fail bringing Dinky back and have the crack close.
Then the Doctor would have been forced to use his Tardis to travel 10,000 years to the future in order to face Dinky as a full grown queen of the ice ponies, which would be much more difficult for him to break the spell and return her to her normal state.
Just wanted to bring that out

Here's a picture illustrating the story
[link]Part 1:
[link]Part 2:
[link]Part 3:
[link]Part 4:
[link]Part 5:
[link]part 6:
[link]Part 7: -You are here-
Part 8:
[link]
Nevermind that now, but that would've been a crazy accident I think.
... Can we see the alternate version some time?