What is Flipside's mirrored counterpart in Super Paper Mario?

Flipside's mirrored counterpart in Super Paper Mario is Flopside.

Flipside is the game's central hub, a town described as existing between dimensions. During the adventure, Mario and his companions use it as a base while traveling through dimensional doors to the game's various worlds and collecting the eight Pure Hearts needed to oppose Count Bleck.

Flopside is not merely a renamed version of the same location. It is a mirrored counterpart that becomes accessible during the second half of the story. Its name follows the game's wordplay: “flip” and “flop” describe opposing sides while echoing Mario's ability to switch between two-dimensional and three-dimensional perspectives. Commonly suggested alternatives such as Flopville or Flipville are not names used for the counterpart. The distinction also matters because Flipside and Flopside function as separate hubs with their own areas, characters, and discoveries.