Gulpin

“Virtually all of GULPIN’s body is its stomach. As a result, it can swallow something its own size. This POKéMON’s stomach contains a special fluid that digests anything.”

— Pokémon Ruby

“Most of GULPIN’s body is made up of its stomach - its heart and brain are very small in comparison. This POKéMON’s stomach contains special enzymes that dissolve anything.”

— Pokémon Sapphire

“This POKéMON’s stomach fluid can even digest scrap iron. In one gulp, it can swallow something that is as large as itself.”

— Pokémon Emerald