Nep-Enut appeared in 1995 video game called Super Mario World 2: Yoshi's Island. Nep-Enut, also known as Giant Nep-Enut, is a water-based, blue counterpart to Gargantua Blargg that hides underwater in the games Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, Yoshi's Island DS, Yoshi's New Island, Yoshi's Woolly World, Poochy & Yoshi's Woolly World and Yoshi's Crafted World. Nep-Enut will remain submerged until Yoshi approaches it. Then, the monster will rise, blocking Yoshi's path. Yoshi must shoot inside Nep-Enut's mouth with an egg for it to submerge in the water (and only its eyebrows will remain visible). If Yoshi jumps over the giant monster, Nep-Enut will give chase.
A particular Nep-Enut in the Super Mario World 2: Yoshi's Island level What's Gusty Taste Like? lives in a secret underground area, and is located entirely underneath terrain and Semisolid Platforms, making it untouchable when it is not in its risen form. The Nintendo Player's Guide specifies this one as a Submarine Nep-Enut, though the actual behavior between the two is the same.
In Yoshi's Woolly World and Poochy & Yoshi's Woolly World, Nep-Enuts only appear in the course, Frozen Solid and Chilled. By tossing three yarn balls into them, Yoshi is able to stun the Nep-Enuts for a few moments. They spit out Shy Guys at Yoshi, which is likely done to give Yoshi an infinite supply of yarn balls to stun the Nep-Enut with. Nep-Enuts can be instantly frozen with an ice watermelon. They can be climbed on during their frozen state, but will release themselves from the ice after a short while. However, Nep-Enuts can be defeated permanently if Yoshi pounds them while they are frozen.
At least one Nep-Enut was originally going to appear in Paper Mario, but was removed from the game for unknown reasons.