A Glitch battle is a type of battle which is initiated by a few types of glitch Pokémon. It happens when an encounter starts with a glitch Pokémon whose sprite causes memory corruption, or, more rarely, when the player has no Pokémon in their team. Glitch battles often feature a series of unpredictable effects. Almost every glitch battle eventually causes the game to freeze. However, there exist mild variants of glitch battles, which only corrupt a handful of addresses and do not cause the game to crash - like 'M's and MissingNo.'s Hall of Fame data corruption.
Glitch battles most commonly follow a constant string of events:
The screen tiles graphics get scrambled, as a result of corrupting the screen data. This step may not happen every time.
The game refreshes the corrupted values and makes the changes visible. This includes Pokémon receiving random status conditions, opponent name changing, or glitchy strings of text appearing on the screen.
Music usually fades into a single sound, or is replaced with static or a low pitched droning noise. Sometimes the low HP beeping loop will start to play for no reason.
The game will try operating on the corrupted values. It may include sending out nonexistent glitch Pokémon, or trying to continue the battle in a glitched state.
Some glitch Pokémon sprites corrupt enough memory to affect the game, but do not corrupt enough to make it unplayable. The most common example is Pokémon Red and Blue's version of MissingNo., whose sprite slightly corrupts the save data by corrupting the Hall of Fame records, but does not destroy any important information.
4(h4? is the most appropriate example, since its encounter sequence clearly showcases all features of a glitch battle.
4 4 crashes the game upon encounter. However, before the game crashes, it is possible to see the glitched battle screen for a brief moment. When it is sent out in a trainer battle, it severely alters the game screen and freezes the game shortly afterwards. It shares these traits with two other glitch Pokémon, 8B 4 8 and ゥ' B.
Yellow form MissingNo.'s front sprite often crashes or freezes the game. It also heavily alters the music and affects graphics after returning to overworld.
♀ . slightly corrupts some memory addresses that are responsible for music and graphics, but generally keeps the game playable.
Certain glitch Pokémon, like PkMnaPkMnゥ ♂ fPkMnk, crash the game instantly and do not give enough time to see any glitch battle effects.
If the player cheats so that they have no Pokémon in their party, they will send out a nonexistent glitch Pokémon in battle, which will inevitably crash the game, but not before totalling the graphics and music.