Vaporeon learnset and teach engine flaw renders Mist as a Day Care only move (Pokémon Yellow)
Another glitch which has become kind of well known, but I haven't documented on video before, and for the sake of single purpose videos (rather than compilations).
Whenever a Pokémon evolves by stone, or levels up via battle or Rare Candy, the game will try to teach it a move defined at the level. Vaporeon is defined to learn both Haze at Level 42, and Mist, with Mist being defined last. Due to a glitch though, Vaporeon only tries to learn Haze. If however you put Vaporeon into the Day Care and walk until it is Level 42, redeeming it will teach it both Haze and Mist.
Incidentally, recently I've updated the page https://tcrf.net/Bugs:Pok%C3%A9mon_Yellow with a list of glitches and/or design flaws specific to Yellow. The pret (Pokémon Reverse Engineering Tools) and Pokémon Yellow disassembly project team likely know issues other than those, which will potentially be for another time.
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Currently, Evie (ChickasaurusGL) 🌺 has 1,196,666 views for Pokémon Yellow across 133 videos. There's close to 18 hours worth of content for Pokémon Yellow published on his channel, or 13.43% of the total watchable video on Evie (ChickasaurusGL) 🌺's YouTube channel.