From Bulbapedia, the community-driven Pokémon encyclopedia.

The Celebi Egg glitch is a glitch that allows the user to obtain Celebi in Gold, Silver, and Crystal. Celebi is an Event Pokémon and therefore is not intended to be possible in normal gameplay.

Discovery

This glitch was first documented at Glitch City Laboratories by user Paco81. It was initially known only as the “Celebi glitch” or “Celebi trick” due to not involving an Egg. However, the Celebi obtained through that glitch would have a nickname and Original Trainer composed of glitch characters and would be stuck at level 100. A variation that allows the Celebi to be hatched from an Egg and therefore largely behave normally in terms of game mechanics was discovered shortly thereafter.

Performance

Requirements

An Egg - The player must get an Egg that will know Beat Up as its third move upon hatching. This can be done by training a male and a female Sneasel up to level 57. Both Sneasel need to have the same four moves in the same order, with Beat Up at position three. Because both parents have the same moveset, the offspring will share this moveset.

A bad clone - The player must get a bad clone, a clone with a name made of only question marks (or, in some cases, blank), its level will be 0 (The glitch will not work if the clone is at any other level, including a more common level 255 clone) and its gender will be different from the prototype's. If that Pokémon doesn't fulfill all those requirements, then it cannot be used for the glitch. This can be done by Pokémon cloning. The Box used for cloning must not be filled at any time as this will prevent bad clones from being created. Getting a bad clone is a case of luck and sometimes occurs during the act of cloning. The chance of getting a bad clone is at maximum if the Box has 15 to 18 Pokémon. Another way to increase the player's chances is by turning the game off after they select YES, before any of the “SAVING... DON'T TURN OFF THE POWER.” text appears.

Any five Pokémon - The player must get any five Pokémon (preferably weak, common or otherwise useless Pokémon). The easiest way to get them is to clone a Pokémon until there is a bad clone. They will get five unimportant Pokémon that may be released.

Procedure

Step 1 - The player must first deposit the Egg into a Box. The five other Pokémon and the bad clone have to be in the party.

Step 2 - The player must then go to the Day Care and ask the man to raise the bad clone. They should then take it back from him, and it will be a ?????.

Step 3 - Next, the player must put ????? at the top of their party and go to the PC.

Step 4 - Using the "Move Pokémon without mail" option, the player must move any Pokémon (preferably a weak or common Pokémon) from a PC Box to the top of their party. Its name should become the name of its original Trainer. The player will now have 7 Pokémon in their party.

Step 5 - Next, the player must go back to the Day-Care Man and ask him to raise the ?????. They should return to the PC.

Step 6 - Back at the PC, the player must deposit the first and second party Pokémon.

Step 7 - Using the "Move Pokémon without mail" option, the player must move the Egg from its PC Box to the top of their party.

Step 8 - Next, the player needs to deposit the next four party Pokémon, but not the Egg.

Step 9 - Subsequently, the player should withdraw any Pokémon that they didn't use for the glitch.

Step 10 - Having completed the set up, the player should walk or bike around until the Egg hatches into a Celebi. However, the Celebi is still unusable.

Step 11- The Celebi will hatch at level 0. Due to how the game handles Pokémon that level up in battle, the player must allow the Day-Care Couple to raise the Celebi to at least level 2. After this, it works like any normal Celebi.

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Explanation

The reason that the acquired Pokémon is Celebi is due to the move Beat Up. In Generation II, both Celebi and Beat Up share the same index number: 251. This is not random and should work with any other move-Pokémon combination. Psychic, whose index number is 94, should result in a Gengar hatching, while Splash, despite being considered the worst move, would ironically bring a Mewtwo, as both share index number 150. This glitch, therefore, should not cause any glitch Pokémon to appear, as there were exactly 251 moves in Generation II, though Ledyba would not be obtainable in this way without using a second potential glitch, as Struggle is unobtainable normally as a move.

?????

If the Pokémon used for breeding has no third attack, the Pokémon that will come out from the Egg (after the glitch) will be a “bad clone” of the glitch Pokémon #000 ?????. This Pokémon, like other "bad clones" cannot be seen by the PC, and hence cannot be deposited in the player's PC or released. There are only 3 known ways to release a "bad clone". One way is to trade it to a Generation I game. Upon arrival, it will become a Generation I original or glitch Pokémon, which may be released normally. The other is to use the PC in the lab on Stadium 2 where the “bad clones” will show up as Ditto or, sometimes, another Pokémon, allowing the player to release it. Recently, a third way has been discovered that doesn't require trading or Stadium 2. The player has to take both the bad clone(s) of ????? (255) and at least one normal, unglitched Pokémon to the Bug Catching Contest on Tuesday, Thursday or Saturday. The unglitched Pokémon should be in first position in the player's party. When entering the contest, the player will be asked to use the first Pokémon in their party and leave the others (i.e. the bad clone(s)) with the contest helper. After the contest has ended the bad clone(s) will be gone, together with Pokémon behind it, even though the contest helper still mentions giving the player their remaining Pokémon back.

If a wild Ditto transforms into the hatched ?????, the wild Ditto is no longer catchable by any kind of Poké Ball. Even a Master Ball will fail to capture it. If a Ditto is bred with the “bad clone” of ?????, the offspring will be another “bad clone”, knowing only Transform.

The “bad clone” of ????? may evolve to a Nidoran♂. Possible levels for evolution are 37 and 62.

At Step 5 of the glitch the player asks a Day-Care person to raise the Bad Clone of ????? (000). That clone will not be taken back until the glitch is finished. After the glitch is finished, that clone will disappear from the Day Care, but on rare occasions, it is possible for that Pokémon to not disappear and remain at the Day Care. In that case the Bad Clone of ????? (000) will be transformed into a Bad Clone of ????? (255). That Bad Clone of ????? (255), similarly to the Bad Clone of ????? (000), cannot be released by the PC, but can still be traded to a Generation I game and released there. It mostly works the same way as the Bad Clone of ????? (000), but it has some differences with it, as it cannot evolve into a Nidoran♂, and if a wild Ditto transforms into the hatched ????? (255), the wild Ditto can be caught normally. It also learns Ice Punch at LV17 and Egg Bomb at LV44, and can learn different TMs and HMs from the Bad Clone of ????? (000). For example the Bad Clone of ????? (000) can learn DynamicPunch (TM01) which the Bad Clone of ????? (255) cannot.

Since ????? (000) cannot be seen by the PC, it cannot be cloned; an Egg that will hatch into it, however, is visible and therefore can be cloned.

Hatched Pokémon's held item

The hatched Pokémon will hold an item depending on the fourth attack of the Pokémon used for the breeding. Both the item and the fourth attack share the same index number. For example, if the two Pokémon used for the breeding have the move Reflect as their fourth move, the hatched Pokémon will hold a GS Ball (or Teru-sama in Pokémon Gold and Silver). This is because both the GS Ball and Reflect have the same index number: 115. If the Pokémon used for the breeding have the move Whirlpool as their fourth attack or Beat Up, the hatched Pokémon will hold the glitch items HM08 or HM09 respectively. Neither of these HMs can be obtained in normal gameplay: they are filler items, and have no corresponding moves. If the Pokémon used for the breeding have no fourth attack, the hatched Pokémon will hold nothing. This is also a way to get infinite Master Balls, which the player can do simply by making the fourth move Pound.

Obtaining a Teru-Sama can be performed with any of these moves: Pay Day, Mega Kick, Growl, Disable, Hydro Pump, StrengthGS, Fissure, Teleport, ReflectGS, Focus EnergyGS, Self-Destruct, SwiftGS, Soft-Boiled, High Jump Kick, Glare, Leech Life, Lovely Kiss, Bubble, Spore, Flash, Psywave, Explosion, Fury Swipes, Bonemerang, Super Fang, Nightmare, Conversion 2, Reversal and Octazooka.

Other effects

Some Pokémon that are deposited in step 6 and step 8 may have their names, gender, level, or attacks changed. Some of them may become “bad clones” and some may remain normal Pokémon. Some of them may also have Pokérus.

When done incorrectly, the Celebi Egg glitch may also result in many code reading errors and Pokémon/character data becoming scrambled. Players may end up with numerous bad clones. Going to the Pokémon screen and looking at the move option will bring up all Pokémon in the party, as usual. However, selecting a Pokémon and going to the Move option will reveal that a ????? is hiding at least 50-80 glitch Pokémon. All of these glitch Pokémon represent the game's code and cause multiple bugs. Therefore, by switching their moves, the game's data, such as music and Pokédex entries, can be altered. The names of these Pokémon vary from ? to random characters and their levels range from 0 to 255. The player's name will also change to a random glitch name. Similarly, the player's ID number will change. The player's original name might be given to Pokémon with many ? in its name, or the names of old player files and Pokémon, and is usually tossed around with junk data (example: ???????GOLD?).

The moves of the glitch Pokémon take data from other parts of the game code. As a result, they usually turn into jargon (example: TYPE/ A9_9[9990979599999999DBB999? ×4 or Waterfall, Waterfall Waterfall, Waterfall or Pay Day, Horn Attack, SonicBoom, Mud-Slap) or just -, and the move's PP will become more than possible or corrupt (ex.: 56/15, 1/35, 86/1). By switching moves around, it is possible to change any data in the game. Since the hidden list of Pokémon is occupying so much space, the game won't be able to load sprite data and the player won't be able to move. While changing moves around, it is easy to access the glitch dimension, or even delete all the player's Pokémon.

This effect of the Celebi Egg glitch is very similar to the TMTRAINER effect in Generation I.



