Biggest difference between Jap and English version

[metal mewtwo]

i think the biggest difference was that in the japanese version when you got all 150 pokemon the game programmer in celedon city gave you mew but in the english version all you got was a crappy diploma :(

[Missingno.Fan]

You got it all wrong

[metal mewtwo]

how am i all wrong

[RaZoR LeAf]

You do not get Mew in the japanese version, it's a lie made up to convince gullible people that they are missing out. People who have played the original japanese versions will agree to this, as they have never received Mew when they got 150 pokemon.

Besides, I think you'll find the biggest difference is the language used. Japanese and English are hardly mistakable for each other.