Igneous Rock Pie and Cloudy Quartz

Igneous Rock Pie and his wife Cloudy Quartz are two Earth ponies who live on a rock farm in Equestria. They are the parents of Pinkie Pie, Maud Pie, Limestone Pie and Marble Pie.

Depiction in the series
Igneous Rock and Cloudy Quartz are first depicted in a flashback in The Cutie Mark Chronicles where Pinkie throws them a party to spread cheer throughout. They all start to smile at it.

Igneous Rock is seen in Trixie's flashback in Magic Duel.

Cloudy Quartz is mentioned indirectly by Pinkie in Make New Friends but Keep Discord, because Pinkie originally invited her to the Grand Galloping Gala.

Igneous Rock Pie and Cloudy Quartz have major roles in Hearthbreakers. In this episode, they are depicted as stereotypically Amish speaking in olde English and traditionalist.

Depiction in the novels
In Pinkie Pie and the Rockin' Ponypalooza Party!, Igneous Rock Pie and Cloudy Quartz visit Pinkie in Ponyville.