So I was watching too many pinkies and I realised pinkie mentioned nana pinkie's stories... Also... In giggle at the ghostly... She sings about granny pie... I wonder... Does this mean pinkie has two grandparents where she got her name... Or... Is it the same pony, named pinkie pie... But is pinkie's grandmother... Ooooor... Is it pinkie breaking the time space continuum and granny pie and nana pinkie are actually pinkie from the FUTURE! (So that's a little far fetched) what do you think? Two ponies or same pony?
If I were to make up a headcanon about this on the spot, the timeline would go like this: A randomly pink pony was born amongst a litter of more drably colored ponies, getting her the name Pinkie; two generations later, our favorite party animal is born the only pink foal of the litter, and so she her parents give her the name Pinkie after her Nana. Then they attach Pie to her name, as well as her sisters Limestone and Marble, to honor Granny Pie on the other side of the family. ...Or, she could've just been spouting nonsense, because she does that from time to time, the silly pony.
