Proto Piranha

A Proto Piranha, originally known as a Gatekeeper and also known as a Proto Piranha Plant, is a large species of Piranha Plant composed entirely of goop. Proto Piranhas appear as enemies in Super Mario Sunshine, Mario Power Tennis, and Mario Golf: Advance Tour.

Super Mario Sunshine
In Super Mario Sunshine, Gatekeepers appear out of Generators in several areas towards the beginning of the game. To get the Gatekeeper to come out of its base, Mario has to spray it with FLUDD until it comes out. In order to defeat one, Mario must use FLUDD to shoot water into its open mouth repeatedly. If Mario sprays one while its mouth is closed, it merely shrugs the attack off. Once defeated, Gatekeepers dissolve into goop, after which their base disappears; Mario cannot wash away a goop base like he can with normal goop. Aside from periodically spawning Swoopin' Stus, a Gatekeeper does nothing to attack, and will actually retreat back into its base if Mario does not defeat it in time. There are three types of Gatekeepers in the game:
 * Pink, yellow, orange, and white Gatekeepers are the most basic variant, needing to be sprayed three times to be defeated. Only one appears at the Delfino Airstrip at the beginning of the game.
 * The brown and white variants are found in Delfino Plaza's square and during the first episode of Bianco Hills, Road to the Big Windmill. Like the above variant, it requires three sprays to be defeated. The one in Bianco Square will send out Swoopin' Stus if left alone, and the one in Bianco Hills sends out Piranhabons rolling down the hill.
 * The black variants are only found in Delfino Plaza, covering the boathouse to Ricco Harbor when the player has three Shine Sprites, and the lighthouse to Gelato Beach when the player has five Shine Sprites. These require six sprays to defeat, and send out Swoopin' Stus. The one guarding the lighthouse will additionally send out a wave of Swoopin' Stus in every direction after the third spray. Additionally, they can replenish goop sprayed away from directly around their bases. However, despite blocking access to new levels, they do not have to be fought as they will vanish upon obtaining a Shine Sprite.

It is also worth noting that the brown one in Bianco Hills is the only one that can be fought multiple times, due to it being the only one in a replayable episode and the rest being fought in Delfino Plaza or Delfino Airstrip to unlock portals to other areas.

Mario Golf: Toadstool Tour
In Mario Golf: Toadstool Tour, the name "Proto Piranha" appears on the leaderboard.

Mario Golf: Advance Tour
In Mario Golf: Advance Tour, Proto Piranhas appear in the Mushroom Course along with many regular Piranha Plants. They are found outside of the course itself.

Mario Power Tennis
In Mario Power Tennis, Petey Piranha's Defensive Power Shot, Piranha Swingback, involves him creating a Proto Piranha to hit an unreachable tennis ball for him.

Super Smash Bros. Ultimate
In Super Smash Bros. Ultimate, Proto Piranhas are mentioned briefly by Viridi during Palutena's Guidance dialogue for Piranha Plant.