Pokémon Red / Blue · Game Boy · 1996 · Impact: Data Loss
Certain in-game glitches — particularly the MissingNo encounter — corrupt the Hall of Fame save data when the player enters the post-Elite Four credits sequence, permanently scrambling the records of their championship team.
Pokémon Red and Blue's Hall of Fame system records the player's party composition at the time of defeating the Elite Four and Champion, saving their six Pokémon's species, levels, and nicknames to a dedicated save block. This block is written during the Hall of Fame entry animation that plays before the credits. When a player has encountered MissingNo or certain other glitch Pokémon during their playthrough, the corruption those encounters introduce into the party data and item slots propagates into the Hall of Fame write. The resulting Hall of Fame entry contains garbled species data — unrecognised IDs, scrambled nicknames, phantom levels — that displays as visual noise or missing entries when the player reviews their record. More severely, the Hall of Fame corruption can bleed into adjacent save blocks depending on how the write is managed, occasionally corrupting the active save file's player name, item quantities, or Pokédex flags. The item duplication bug associated with MissingNo — which inflates the sixth item slot quantity to 128 — does not directly cause the Hall of Fame corruption, but players who used MissingNo encounters specifically to duplicate Master Balls or Rare Candies before an Elite Four attempt frequently discovered the corruption on their Hall of Fame entry, associating the two bugs in popular understanding even when the mechanisms were distinct.
Pokémon Red and Blue's save system allocates fixed-length blocks for each data category: player info, Pokédex, item bag, PC boxes, party, and Hall of Fame. These blocks are written sequentially with minimal boundary checking between them. When a party slot contains a glitch Pokémon like MissingNo, the slot's species data is a value the game's save routines were not designed to handle — they write it faithfully to whatever byte offset corresponds to that slot's position in the party block.
If the species ID or associated data field is large enough to overflow the party block's allocated size, the write continues into the adjacent block — which, depending on the save memory layout, may be the Hall of Fame data or the player's personal info. The Hall of Fame write that occurs after defeating the Champion then attempts to read the party data for recording and encounters the already-corrupted fields, writing their garbled contents into the permanent Hall of Fame record.
Because the Hall of Fame block is designed only for reading after the initial write, the game has no mechanism to detect or correct the corruption. The scrambled entry persists indefinitely in the save file.
The Hall of Fame corruption was one of several linked bugs that players encountered through the MissingNo route and reported to Nintendo in the years following Red and Blue's release. Nintendo's official response distinguished between the item duplication bug — which it publicly acknowledged and cautioned against — and the Hall of Fame corruption, which it did not formally document in consumer-facing materials despite being aware of it internally.
For many players, the Hall of Fame corruption was their first direct experience of data loss from a bug rather than hardware failure or deliberate deletion. A corrupted Hall of Fame entry after an Elite Four run — which for many children represented weeks or months of play — was a genuine emotional event, and the community's documentation of how and why it occurred was among the earliest examples of systematic player-driven bug analysis in a major franchise. The thoroughness of that analysis, shared on early forums and fan sites, established a model for Pokémon glitch research that continues in Generation I communities to this day.