Flipside is the main location in the game Super Paper Mario. Merlon is the leader of Flipside. It is said that it was created by Merlight. It's counterpart is Flopside. Mario must collect all the Pure Hearts in order to stop the dark void in Flipside from growing and destroying it. There are many shops in Flipside, such as Howzit's, Itty Bits, and Catch a Dream. Many events also take place in Flipside, such as Mario meeting Tippi, and Mario finding the first Pure Heart, which Merlon gives him. Peach also joins Mario's party here, after escaping from Castle Bleck. Saffron makes recipes here.
In Flipside, you must find each of the 4 Heart Pillars and set the Pure Hearts in them. In Flopside, you must do the same.
Flipside visit 1: You get introduced to Flipside. You become the hero and find the 1st Pure Heart.
Flipside visit 4: You get introduced to Flopside and set the 4th Pure Heart in the final Flipside Heart Pillar.