During the events of "Secret of My Excess", Twilight takes Spike to the veterinary, Mane Goodall, to see if she can cure his sudden growth spurt. However, Goodall loves dragons, and has a special treatment for him in mind...

Outline by Bronystories
Written by Nostalgia Schmaltz

Also, I have no idea what the vet pony's name really is. I'm just going with the name for her that I was given.