SpoilerNana is a term for grandmother, so Nana Pie and Granny Pie are probably the same pony.
SpoilerThis is a world where inhabitants can use literal magic, fly, sleep on clouds, move faster than the sound barrier under their own muscle power, produce light while doing the same, and run full-force into solid rock without injury. We either need to assume that some of the stuff on the show is just there for visual gags, or assume some really lenient laws of physics.
And as for apples and oranges, it seems like Applejack's family feud is so strong is affects the rest of reality.
SpoilerLooks like Sapphire Stone again.
Listen again. "Pinkie Pie" said she was going to Applejohn's barn raising.
SpoilerIf I am recalling right, one is Apple Fritter, one of the ponies that Applejack introduced in the first episode. I don't recognize the other right off hand.
SpoilerNow we need a story where Equestria gets crossed with a world full of sentient oranges.