|Bulbapedia also has an article about Pokémon Crystal.
Similar to Pokémon Gold and Silver, Pokémon Crystal has a large number of minor glitches (most of which inherited from Gold/Silver), but is surprisingly hard to break, especially since the Coin Case glitch is fixed in Crystal. The bad clone glitch (as well as normal cloning) still exists, and in addition to party-shifting exploits (most famously the Celebi Egg trick), the bad clone can be exploited to achieve ACE with a newly introduced glitch in Crystal, 0x1500 control code arbitrary code execution. In fact, the latter exploit is arguably easier to achieve since it does not require a "real" bad clone (one with 0x00 as the second species byte), just any corrupted clone with an unterminated name.
Wrong pocket TMs and HMs still exist in Crystal, but similar to in Gold and Silver, they are relatively difficult to obtain, ultimately requiring either the bad clone glitch, or trading with an already broken game (which usually allows setting up 0x1500 ACE as easily), or other obscure glitches that are likely even more difficult to perform.
Even though Crystal's game engine is largely built upon that of Gold and Silver, from the viewpoint of trying to break the game, it is quite different since the Coin Case glitch is fixed. Therefore, the bad clone glitch is the main entry point for breaking the game in Crystal. On the plus side, the existence of 0x1500 control code arbitrary code execution means that a "pseudo" bad clone (one where the species bytes are not corrupted, but the nickname is corrupted) can still directly lead to ACE.
However, since the setup for 0x1500 ACE is fairly complicated, some players may instead simply use the unterminated name of the "pseudo" bad clone to do memory corruption with buffer overflow, in particular to get a "real" bad clone. From there, the bad clone can be exploited with the same methods as in Gold and Silver, leading to arbitrary Pokémon, items, etc. and even wrong pocket TM/HM ACE.
The Battle Tower SRAM glitch, usually combined with the God Egg glitch, is the counterpart of Gold/Silver's Hall of Fame SRAM glitch (which is fixed in Crystal). It requires the player to play through the game twice up to the Battle Tower, the second time without ever saving the game after getting the starter. However, since the Coin Case glitch does not exist, the Battle Tower SRAM glitch is actually the only known way to break the game without save corruption (defined as interrupting the saving process by hard resetting) or external assistance (e.g. trading with another game). As such, it is the base for the only known (glitched) route for the Crystal any% No Save Corruption speedrun.
- Documentation of bugs and glitches in Crystal in the pokecrystal disassembly project
- The Bad Clone Trick page on PRAMA Initiative