Character ID

ID Pokemon are pokemon that appear to a player based on the secret ID number that they have.

To recieve the other pokemon it is needed to go into the dungeon with a player that spawns said pokemon. When both players go into the floor with the pokemon that spawn the players will see both of them at the same time.

Qualifications
The qualifications to be an ID Pokemon is to be in a set, such an example is Plusle and Minun. These Pokemon tend to have relationships with one another. The most common one is if the pokemon have some sort of relationship whether it be strong friendship or bitter enemies.

Location
ID Pokemon can appear in any number of dungeons. The pokemon that appear are as follows; Plusle and Minun spawn at the same floors in Thunderstorm Forest floors 6 to 10. Seviper and Zangoose spawn in Winden Forest at floors 8 to 18.
 * Plusle/Minun
 * Seviper/Zangoose

ID Items
While ID Pokemon are the more common and more popular there are ID Items. These items appear based on the player ID and spawn randomly in dungeons. To see the other item you must go with a player to the dungeon and both items will spawn at the same time (Spawn rates are independent and cannot be influenced by players).

The current items that are ID Items are shoal shell and shoal salt made to form shell bell. These items are found in Southern Sea from floors 16 to 28. These items appear visible on the walls.
 * Shoal Shell/Shoal Salt

Affect your Secret ID
There is a way to affect the secret ID that you get and thus the ID Pokemon and ID Items that you can see. The only way to affect is to current knowledge is the starter you choose, for example if the player picked a Shinx, that player will see a Minun in Thunderstorm Forest, and not a Plusle. However if that player picked Cyndaquil, then the said player will see Plusle, and not Minun.

There is no way to see both ID Pokemon or ID Items at the same time without another player's assistance.