Little to None
This bug is the only Pokemon that will straight up die if it comes into contact with any form of damage because it has literally 1 HP.
What is Shedinja?
Hatching from an egg during the Indigo League, this would go on to be Misty's most well known and popular Pokemon.
This cool sounding move unfortunately is not very useful, as it is only learned by Octillery and is effectively just a worse Muddy Water.
What is Octazooka?
While this glitch goes by a few names, this aptly named version of the glitch allows you to catch a Mew in Pokemon Red and Blue.
What is The Mew Glitch?
This theory proposes that none of the Pokemon anime actually happened, and instead all took place is a comatosed Ash Ketchum's head.
What is the Ash Coma theory?
This Mythical is the only Pokemon to be listed as 000 within the Pokedex, as it is in the Unova dex.
What is Victini?
Despite being one of the first Pokemon we see in the Pokemon anime, this bird would not be fully debuted until Pokemon Gold and Silver.
What is Ho-oh?
This move gives you item to the opponent. Without doing damage. That's it. Just use Fling.
What is Bestow?
While this technically isn't a glitch, this "Pokemon" could only be seen if you were to use glitches or a cheating device. It also does this fun little thing where it crashes your game, corrupts your save file, and deletes it. Shouldn't have cheated 4Head.
What is Bad Egg?
This theory proposes that Ditto is a failed clone of Mew as the have a large list of similarities and connected circumstances that can't just be written off as coincedence.
What is the Ditto is a Failed Mew Theory?
This ghost type Pokemon is tied with 4 others as the lightest Pokemon. Makes sense. It's literally a ball of gas.
What is Gastly?
Aside from Lucario there were other Gen 4 Pokemon that appeared in the Mystery of Mew movie, including this evolution of a gen 2 Pokemon.
What is Weavile?
This fighting type move's power doubles if it hits a paralyzed target. This is the Hariyama lines signature move.
What is Smelling Salts?
Due to a funny little quirk in Pokemon Emerald's code, this berry could allow you to do whole host of different glitches and exploits, all under the umbrella of this glitch.
What is the Pomeg Glitch?
This theory claims that you are the reason one Blue's Pokemon dies in Red and Blue. He has no other reason to care about the Lavender Town Tower as does not fight against Team Rocket at all throughout the games story.
What is the Dead Raticate Theory?
This is the first Pokemon listed by Red and Blue's index numbers, meaning it was the first Pokemon coded into the game.
What is Rhydon?
Two of this Hoenn Pokemon actually appear in the Johto League anime. It's fair if you missed it though. They are camoflauged after all.
What is Kecleon?
Despite no Pokemon being able to learn this move in Pokemon Red and Blue, it was intended to be the Abra lines signature move. It's like Flash, but if it could miss for some reason.
What is Kinesis?
Using the power of the calculator in the Gen 4 games allows you take advantage of this glitch which, with proper use and navigation, allows you to catch event exclusive Pokemon without having to time travel back to a Toys R Us.
What is The Void Glitch?
This theory/creepypasta claims that hundreds of a children were driven to self ending tendencies due to the frequencies of Lavender Town's music in Pokemon Red and Green. However a quick Google search and a little bit of common sense will unveil that Nintendo did not had to sweep the death of hundreds of children under the rug.
What is Lavender Town Syndrome?
Due to an oversight in Gen 2's coding, if this Pokemon Swords Danced one too many times while holding its signature item, it's attack will roll over to a ridiculously low number.
What is Marowak?
This is one of, if not the only, Pokemon that was unveiled before it's generation that is actually able to be used in battle as you are able to use it in Pokemon XD's Battle Bingo mode
What is Bonsly?
Of the many multi hit moves that have been designed this one could only be learnt by two Pokemon, Exeggcute and Exeggutor.
What is Barrage?
This nifty little gambling tool also doubles as Action Replay or Game Shark in the Generation 2 games. Anything a cheating device could do, gamba could do it better.
What is the Coin Case glitch?
This theory/creepyasta claims that the boss of Lavender Town Tower was meant to be a rotting corpse with two White Hands as Pokemon instead of the Ghost Marowak. Upon losing the battle, the corpse would eat the trainer on a game over screen.
What is Buried Alive?