This story is a sequel to Petriculture

It's been several months since Pinkie Pie made a stunning admission about her past that permanently changed her relationship with her friends, particularly Twilight Sparkle, but life seems to have settled back to normal (well, normal by Pinkie Pie's standards, at least). However, when an old nemesis returns and ensnares Twilight in her influence, it's up to Pinkie to make things right.

This is the second story in The Petriculture Cycle. There is a TV Tropes Page for the entire Cycle here.

Cover image by Page Turner; "Princess Twilight" vector by Nianara.

Perhaps Doctor Whooves is not a medical doctor or a time lord, but a doctor of psychology.

The following are his journals after he receives instructions from Princess Celestia to permanently set up shop in Ponyville to keep an eye on Twilight Sparkle and her friends, where he learns more than he bargained for.

View the Google Docs table of contents: https://docs.google.com/document/d/1gCeHce9BTZ48P5fxNQDHq7diYlNqJIbkZNdMGLN3H5k/edit?pli=1

Humans.

Truth or myth? Ancient lost civilization or just an old pony's tale?

No pony has ever seen one, and most haven't even heard of them. But Lyra knows that these wonderful creatures are more than just old legends, and she's going to find out... and possibly drive her roommate insane in the process.

“I've met lots of magic ponies. Even singing ones. I've met everybody.” - Death, DC Action Comics #894

Death comes to all things. Stars, gods, people, and even ponies. She rarely visits Equestria, but it's one of her favorite places. Something about the harmony there. And ponies almost always die when they're very old, which is a nice bonus. But she knows that makes it harder on the ponies left behind, most of them aren't used to death. So sometimes, while she's there, she takes the time to enjoy her visit, and to try to help everypony there to deal with something that seems so strange to them, but so normal to her.

Three part crossover with Neil Gaiman's Sandman universe. But the only thing you really need to know is that Death is the personification of death across all universes, and usually appears to humans as a rather cheerful teenaged goth girl.