Caves are the underground areas in Pikmin 2, of which 14 exist in all. Although there are several overground areas, most treasures are found in caves, so most of the time playing the game is spent down them.
The time of day does not pass while the player is in a cave, and their floors are generated randomly each time, but follow a specific layout scheme. According to earlier versions of the game, this is because the space-time continuum was warped due to the cave's geomagnetic radiation field. The final version's instruction manual simplifies this and simply calls it "a powerful magnetic field".
Caves are entered though holes. To enter one, the player must press / while near it. If the other leader is alive, it'll instantly join the party, regardless of distance. Any Pikmin under the current leader's control will jump down with them, and any that are idle, working, or on an idle leader's group will return safely to their Onions. Once the player enters a cave, there is no way to increase Pikmin population save for Bulbmin and/or Queen Candypop Buds. It is not possible to enter a cave without Pikmin.
Most objects respawn between visits to the same cave, including enemies. Treasures will not reappear once collected, and some Candypop Buds that have a maximum Pikmin requirement will also not show up.
Inside a cave, if both leaders lose all their health or all Pikmin die, the research pod will cancel the expedition, losing the collected treasures in the process, and then bring them to the overworld. A mission can also be aborted manually by using the pause menu.
The other Pikmin games do not have caves like the ones in Pikmin 2, but have underground locations regardless. Pikmin has The Forest Navel, Pikmin 3 has underground sections within its main areas, and Hey! Pikmin has some cave-themed levels.
List of caves
Each cave is divided into several sublevels. Each sublevel consists of a small area, that gets randomly generated every time it is entered, and will usually have at least one treasure and a few enemies. The shortest cave – Emergence Cave – has two sublevels and the longest – Hole of Heroes – has fifteen.
When a cave is entered, the player will land in its first sublevel, and will be able to proceed through that cave's sublevels in order through the use of holes. When, / is pressed near a hole, all Pikmin and live leaders will jump down the hole, landing in the next sublevel. Planted Pikmin will remain in the same sublevel and be lost forever. Some sublevels have geysers that allow the player to safely leave a cave from that sublevel.
Every time a sublevel is entered, the game is saved, so if the player turns the game off and then back on again, they will start in the same sublevel, but it will be generated randomly again.
Sublevels can be roughly categorized into three types:
Normal levels usually have a few harmful enemies, and sometimes don't have any treasure.
Rest levels either lack enemies or only have harmless enemies (exceptions being Doodlebugs and Bulbmin). Rest levels have Pikmin-supporting items, such as nectar, ultra-bitter spray, ultra-spicy spray, or Candypop Buds. These levels usually lack treasures, and feature special ambient music. Most rest levels also have a geyser available, so the player can return to the surface if they have a low number of Pikmin.
Boss levels contain one or more large bosses, are usually the final level of a cave. The only cave without a boss level is the Emergence Cave, and the one with the most is the Hole of Heroes. When the boss is defeated, it often drops an upgrade for the leaders' space suits or ship.
The deepest sublevel of every cave is known as the final floor in the US version, and the final level in the European version. In all caves except for the Emergence Cave, the final floor is a boss level, as described above. In every case, since there are no deeper sublevels, all final floors contain a geyser for the player to use to return to the surface and end their cave mission. These geysers are usually placed to be easily accessible before the boss arena, making most boss battles easily skippable, at the cost of missing the boss's upgrade. The boss will remain present until it is defeated; the player can always return at a later time.
As the player drops into the final level, the game announces this fact by playing a distinct jingle, along with displaying the words "FINAL FLOOR!" in large, yellow letters, before the player regains control. Additionally, on the HUD, the word "SUBLEVEL" in the top-right corner is replaced with the words "FINAL FLOOR" in yellow.
To enter a cave, the leaders and Pikmin must dive into a hole. To go from one sublevel to the next, they must also go down a similar hole.
The holes are round, rocky mounds, with a small hole in them. On the cave entrance hole, if the cave has uncollected treasure, wisps of steam will come out, and the screen will become foggy when the hole is approached. Inside a cave, the hole to a next sublevel will always contain steam, but will not fog the screen.
To enter a hole, the player must simply press / when their leader is close to it, then confirm this action in a dialog box.
Even though most sublevels are randomly generated, there are consistent themes shared between them. The following is a list of themes used in the game, based on what the units are called in the game's files. The screenshots are from Challenge Mode stages, not story mode caves.
Some caves have a background (also called a "skybox", or "VRBOX", as they're known internally), as a wall and/or bottom way off in the distance. Because they're so far away, it may be hard to see them over the fog and lighting. Designs that are meant to give off the idea that the leaders and Pikmin are enclosed in a burrow do not have a background, but other sublevels normally do. There can be any sort of sublevel theme and background combination.
When a sublevel is entered, the game generates it randomly; it starts by building random terrain, and then populates it with random objects.
A sublevel's terrain is composed of several cave units stitched together. Each unit can be a dead end, a corridor, or a room, and has some spots where objects can spawn; each spot contains data about the amount and type of object that can spawn there. In each sublevel's configuration, there is data about which cave units it is allowed to use, and data about how the dead ends, corridors, and rooms should work in terms of quantities. The game then uses this information to randomly create and connect cave units.
Each sublevel's configuration also has information about what objects to spawn. Entries listed in this information specify what type they are, what object to spawn, a minimum amount, a random filler weight, spawn location, and some other properties. Depending on these properties, different entries are processed differently by the game. With this in mind, entries can be thought of as belonging to one of five different "categories". As a general rule, the "main" category contains enemies, the "decorative" category contains plants, the "treasure" category contains loose treasures, the "gate" category contains gates, and the "dead end" category contains objects specifically meant to appear in dead ends.
On the wiki, each sublevel section in a cave's article contains a basic list of objects that can spawn, as well as their amounts. It also contains a more detailed list that explains what objects the game wants to spawn, in what order, and under what details. These lists reflect the sublevel's data in the game files. Though the basic list can be changed to better document what really happens in-game, the detailed list always reflects what the sublevel's data says. In the detailed list, the ID of each entry is not something recognized by the game, but exists to make the list easier to understand.
After generating the sublevel's layout, the game follows a complex process to spawn objects in it. The following is an outline of this process:
Because the sublevel generation doesn't use many fixed numbers, and instead opts to use statistics and randomness to generate diverse sublevels, the game can create a sublevel where some objects in its generation data do not spawn. Sometimes an object has a minimum amount of 0, and as luck would have it, it was never chosen when filling out objects at random. At times however, a sublevel may physically be unable to accommodate some of the intended cave units or objects. For example: Frontier Cavern sublevel 4 wants to spawn a Violet Candypop Bud (in a dead end). In one attempt, the generated sublevel has 4 dead ends, so both treasures, the hole, and the Violet Candypop Bud appear in dead ends. But in a different attempt, the game generates a sublevel with 3 dead ends – only the treasures and hole will have a spot, and the Violet Candypop Bud will not show up. This happens often with decorative objects, but can, in rare cases, happen with important objects. Players should be wary about this possibility, and if they find an important item is missing, they can reset the console and try for another sublevel layout.
Scenarios that can make an object not appear include:
Note that when the sublevel has finished generating, the game may purposely delete some objects for gameplay reasons. This happens to treasures in Story Mode that have already been collected, and Candypop Buds that do not meet the maximum Pikmin requirement.
Cave entrance leader mixup
When entering the first sublevel of a cave, the game may or may not switch the player's active leader. This does not happen when the player goes from one sublevel to the next, making it mysterious as to why the leader changes seemingly randomly when going to the first sublevel.
In reality, this happens because of a simple glitch. In order to decide what leader to turn active whenever a sublevel is entered (be it the first or not), the game reads a variable in memory. This variable is also saved onto the save game data and loaded from it. It is set whenever the player goes from one sublevel to the next, which explains why, when the next sublevel is loaded, the game selects the correct leader. However, this variable never gets set when the cave itself is entered. This means that when the first sublevel is finished loading, the game reads the variable, and uses an outdated value, last updated when a sublevel hole was entered. This glitch was not fixed for the New Play Control! rerelease.
It can also be noted that Challenge Mode uses a different behavior, without a glitch, and that the default value of the variable is 0, meaning that at the start of the game, before the player goes from one sublevel to the next, the game will make Olimar the active leader when entering a cave.
Hole entrance grunt mixup
When entering a cave or sublevel hole, each leader grunts as he jumps. However, the first leader to jump will always make Olimar's sound effect, and the one behind will always make Louie's, regardless of the existing leaders and their order. The only exception is if the second leader is fallen, at which point only the first leader will grunt, still with Olimar's voice.
Even though the cave and sublevel information is present in human-readable format within the game's files, some of their settings appear to make no sense, as the values in the files don't match up to what happens in-game. The following assumed discrepancies have been noted: