Inside Buu is the inside of Super Buu.
The inside of Buu is first seen when Super Buu absorbs Vegito, while the Saiyan fusion was protected by his Saiyan Shield. The Potara fusion could not be supported by the environment inside Buu, and was nullified. Separated, Goku and Vegeta explored the inside of Buu. They fought enzymes, a roundworm family, illusions of Gotenks, Gohan and Piccolo, and Super Buu materialized inside himself. Then, they freed their friends and sons from Super Buu's body, as well as the fat Majin Buu, before escaping Buu's body.
The inside of Super Buu is explored in Dragon Ball Z: Buu's Fury. Goku and Vegeta visit Buu's stomach, intestines, and brain. Enemies encountered there are blood cells, blisters, enzymes, and roundworms.
- The area from the stomach that leads to Buu's brain is called intestines in Buu's Fury, while it should have been called esophagus to be consistent with regular anatomy.