Celestia is tired of Canterlot having crummy coffee. No ponies seem to know how to make a good cup of joe! Maybe she needs to steal some coffee secrets, and manpower, from another world...
I've been stuck as Rainbow Dash for little over two months now, not sure how, but it happened randomly. Being from the "one percent' group of wealthy people, parent's didn't notice or care... they probably don't even know I somehow got to Equestria.
A human of low character dies and gets sucked into Equestria as a copy of Twilight. The new mare then proceeds to cause chaos for the ponies, but she tries to help... and, more importantly, make some money
When John Radderson ended up as an anthropomorphic alicorn Princess Twilight Sparkle, she set off a chain reaction that transformed her classmates into her pony friends.
An unwilling non-brony traveller from Earth finds himself switching between bodies of the Ponyville locals randomly, leaving so much chaos and confusion in his wake that Discord might as well retire now.
Woke up, everyone's gone, and I'm some kind of alien horse. Well, not everyone, I did find another: a baby. A baby alien horse that treats me as her mother.
Linda settled for bed, only to awaken in the middle of a garden of statues of horses. She was one of them, only not so stone. When she eventually slumbered there, she returned home. Living two lives, can she make sense of it all? Fix it, or enjoy it?
After his sudden death on his way to school due to an idiot driver, Ken Williams wakes up to find himself as a strange quadruped with wings and a horn.
Something one does not want, is to have a bad day at work, then wake up as a pony, not when said pony is sore and battered and has an odd feeling in her abdomen