Gut Check (location)

Gut Check is an area inside of Bowser's Body in Mario & Luigi: Bowser's Inside Story. It is apparently located in Bowser's Stomach. When the Wiggler challenges Bowser to eat the giant carrot, Mario, Luigi, and Starlow come here to help him digest the carrot. The player must tap on each piece of carrot three times to make it disappear, and when all the carrot bits are gone, Bowser will eat more. The player must finish the entire carrot in less than one minute to proceed.

Also, Mario and Luigi come here a second time to get the second Star Cure after Bowser swallows it.