How to find MissingNo. in Pokémon Red

To find MissingNo. in Pokémon Red: watch the old man's catching demonstration in Viridian City, fly straight to Cinnabar Island without walking through any grass or caves, then surf up and down the east coast of the island. The glitch works in Pokémon Claude Red exactly as it did on the Game Boy.

Steps

1. In Viridian City, talk to the old man (after he has had his coffee) and answer that you're not in a hurry. He shows you how to catch a Weedle.
2. Get to Cinnabar Island using FLY, without walking through any tall grass or cave on the way (Surfing on sea routes is fine if you don't touch grass).
3. Surf onto the water on the east edge of Cinnabar Island and move up and down along the coast tiles.
4. A wild battle starts: MISSINGNO., 'M, or even a high-level Pokémon, depending on the letters in your name.

Why it works

When the old man shows you how to catch, the game backs up your name into the memory that normally holds the local wild Pokémon list. Only areas with tall grass overwrite that list. The shore tiles on Cinnabar's east coast take their encounter rate from the water but their Pokémon list from that leftover memory, so the letters of your name are read as levels and species numbers.

What happens when you meet it

• The sixth item in your bag gains 128 (see the item duplication glitch).
• Catching MissingNo. can scramble the Hall of Fame records.