Pit

Because this subject has no official name, the name "Pit" is conjectural.

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Pit (also called bottomless pit, abyss or void) is the name given to the depths down below where the level is on top of. In games, these pits usually kill or harm creatures that fall into them, and for the most part, their bottom is unknown. In the Pikmin series, a pit's punishment on an object that falls in depends on a variety of factors.

Most areas are considered to take place at ground-level, but some areas and caves clearly take place suspended above a seemingly endless abyss. There are borders almost everywhere stopping creatures from just walking off the edge and falling down, although some enemies can take steps large enough to walk over these boundaries, and leaders can throw Pikmin or their own partners over the boundaries.

Technically, all levels contain a bottomless pit – environments that appear to be at ground-level simply keep a pit plane right under the ground. This can be proven by the fact that, in some extraordinary cases, Pikmin or leaders can go through the ground, and will act as if they had fallen into a regular pit.

Locations

The following is a list of areas, caves and levels that contain clearly defined and accessible bottomless pits.

Pikmin

The only location in Pikmin with a normal abyss is The Forest Navel, where throwing Pikmin off the stage is a possible issue.

Pikmin 2

None of the overworld areas in the game have a regular abyss, but cave sublevels with the "metal" theme take place in rusty platforms suspended by metal beams far above the pit. The following caves have such sublevels:

Story mode

Subterranean Complex, sublevels 2 to 9.
White Flower Garden, sublevels 1 and 2.
Snagret Hole, sublevels 4 and 5.
Cavern of Chaos, sublevels 1 and 2.
Hole of Heroes, sublevels 12 and 13.
Dream Den, sublevels 3 to 5.

Challenge Mode

Brawny Abyss, both sublevels.
Collector's Room, sublevel 3.
Cave of Snarls, sublevel 2.
Secret Testing Range, both sublevels.

2-Player Battle

Pikmin 3

The only way to access abysses in the main mode is through glitches that push objects under or off the level. In Mission Mode and Bingo Battle however, pits exist in the same fashion as in Pikmin 2, that is, as the area below metallic levels. In Mission Mode, this is Clockwork Chasm, and in Bingo Battle, this is the Rusted Labyrinth and Corroded Maze.

Behavior

In general, pits are meant to kill whatever falls in, but for gameplay reasons or due to oversights, this may not always be the case.

Leaders

To do: Add the Pikmin glitch to the glitches article, and expand on the Pikmin 3 info (plus, what about the Bingo Battle stages?).
Care to do so?

In Pikmin, Captain Olimar is not meant to fall into the void that surrounds The Forest Navel. However, it is possible to exploit a situation that can allow Olimar to walk off an otherwise-unreachable edge: by having a Shearwig chew off the bridge connecting the main land to the island on the northwest while Olimar is on said island, the bridge will slowly be removed, revealing the walk-off ledge to the captain. Alternately, Olimar may be pushed off the stage by being compressed against a 20 pellet^[1]. As the game is not ready to handle Olimar walking off, he will not be killed but will instead continuously walk on an invisible plane. He will keep moving forward, something which cannot be controlled by the player. In some unused maps that have floors that can be walked off, the same behavior happens. Oddly, on The Forest Navel, Olimar also teleports some distance above ground level when he goes out of bounds, and when he bumps against a wall or there is terrain below him, he begins walking in a different direction at almost twice his previous speed. If in this state, he goes above other pieces of terrain, he'll simply fall on them, going back in-bounds.

In Pikmin 2, it is easier for leaders to fall into the void, although still only in unintended ways. If a leader falls off, he will just reappear back on the main land without problem. The exact spot he appears on depends on the stage, but for the Awakening Wood and the Perplexing Pool, it leads to otherwise-unreachable paths. In order to fall into the abyss in an area, a glitch must be abused, like the seesaw block glitch. To fall off in a cave, the leader must be carried by a dweevil, although this could result in a much more dangerous glitch.

In Pikmin 3, falling into the abyss was hard, but possible, prior to the 1.4.0 update. Before said version, leaders could only touch the pit plane by glitching into walls. Much like in Pikmin 2, leaders that touch the void are merely respawned back in a specific location, which can be used to skip portions of the area. After the aforementioned update, leaders started taking damage when falling off (one third of their maximum health), and would respawn back on the stage, although in a different place than before, removing some exploits.

Pikmin

Pikmin that fall into the abyss will be killed. In Pikmin 3, their death scream is long and high-pitched, clearly noting that they have been thrown into one. Although rare, it is possible for Pikmin to touch the pit plane on seemingly "pitless" areas, via a glitch such as the crushing glitch.

Enemies

In the first two games, enemies that fall in a pit are killed right away. If the enemy was carrying a treasure, said treasure will just reappear on the stage.

In Pikmin, the only way to see enemies fall off is by luring a Shearwig into an area with a low boundary, damaging it, and hoping it flies over it. Other than that, there is a notorious glitch with the Beady Long Legs, in that if it escapes its arena, and is lured to the bottomless pit near the section with the Libra, the game will freeze.

In Pikmin 2, the boundaries on some of the metal-themed cave sublevels are low enough for large enemies to cross over, such as Gatling Groinks and Fiery Bulblaxes. These enemies can be made to cross the edge by having prey on the other side; they'll walk off while attempting to chase their target. This can be exploited in order to kill the enemies easily and without consequence.

For Pikmin 3, the rules were changed a bit: enemies that fall off the edge are put back onto the ledge that they fell off of in a similar way to that of the leaders. The enemies, however, do not take any damage. This is observable in Mission Mode in stages such as the Clockwork Chasm, and in Bingo Battle in stages such as the Corroded Maze.

Other objects

To do: Explain what happens to the cursor in each game – does it disappear (sinks to the bottom of the bottomless pit), or does it stay on an invisible plane at ground level?
Care to do so?

Ship parts that fall into a pit will not return. This is normally not a problem, but the Libra has the potential to fall off the island it is at while being carried, and if it falls into the void, it cannot be recovered.

Treasures that fall off will simply reappear somewhere on the cave. This is true for treasures being carried by Dweevils or treasures that are inside undefeated enemies.