Flopside is the near-exact reversal of Flipside in Super Paper Mario, much like looking into a mirror. Flopside was created by both the Tribe of Ancients and the Tribe of Darkness as an antithesis to Flipside. It was first realized that without darkness (as Flipside was a town of light), Flopside would fall into ruin, as light cannot exist without darkness. As a result Flopside was created as a town of darkness to offset Flipside. The two towns are in perfect balance and have been ever since.

The denizens of Flopside are mirror versions of those in Flipside. Usually they feature different color schemes and opposite personalities. Exceptions include Nolrem, who shares the same personality and role, if not coloring compared to his counterpart Merlon. Likewise, the town's layout mirrors Flipside, differentiating itself through unique puzzles and shops throughout.

Flopside Tower serves as the only access point to Count Bleck's castle in the game's final chapter. The large black door can only be accessed after Mario acquires all eight Pure Hearts. This town was destroyed by The Void when Super Dimentio accelerated its expansion.