Hayseed Turnip Truck briefly appears during Season 2 Episode 9 Sweet and Elite, while Rarity is speaking to a couple of upper-class ponies at a cafe inquiring about where she got her hat. Before Rarity can answer, Hayseed Turnip Truck yells out to her (as he appears to be cleaning windows as a job in Canterlot) and falls down, and then continues to embarass Rarity in front of the upper-class ponies. Hayseed Turnip Truck is essentially a "hillbilly pony", remarking to Rarity how they met at the "Big Hoedown in Ponyville!". He also sports typical hillbilly associated features, such as a turnip hat (Likely to represent a typical green John Deere Tractor hat), stained shirt, as well as buck teeth, mullet hair, and a very distinct style of "redneck speech". He compliments Rarity by saying that she likely made her hat herself, and revealing that she is from Ponyville (to the sneering of the upper-class ponies). Although he is extremely happy to see Rarity, she does not appear to feel the same considering the ponies that were inquiring about her hat were considerably "high class". It is likely that Rarity was friends with Hayseed Turnip Truck in Ponyville, but in the context of her stay in Canterlot, it was unwelcomed as she tried to assimilate with the upper-class crowd.
In Season 3 Episode 9 Apple Family Reunion, Hayseed Turnip Truck is briefly seen at the beginning of the reunion and is even included in the family photo, suggesting that he is a member of the Apple Family.