You only get a diploma for catching them all.
Professor Oak gives you a diploma...that's pretty much it.
you be come the Pokemon master
Congrats for first second go to prof oak just watch what happens it will scare you.
Nothing prof oak thanks you and that's it.
I have caught the 150 original Pokemon myself and all I got was some praise from Oak, but if you are talking about all on the national Pokedex, then I have no idea!
For a player to complete the Pokedex in the first generation games Red and Blue, they must catch all 150 official Pokemon from the first generation. After this, they receive an in-game certificate and congratulations from Professor Oak.
If you get all the Pokemon and 99 of all items you can restart the game and be Jarachi as a starter.
You have basically completed the game. You can also get the 151st Pokemon (Mew) but you can only do it through an in game glitch (search it on YouTube) or by using a cheat device. You can also go to Celadon City and go to the Large Building and talk to the Game Designers the game creater will give you a diploma whether you have caught 150 or 151 Pokemon.
You realise how much time you have wasted looking for them all.
Well when you SEE all 150 Pokemon prof. Oak will give you a deploma then go to cinnibar island and head inside and talk to bill...and be ready for an adventure!! Then when you own all 150 Pokemon you can get the mystic ticket! (which you can only get in an event) this allows you to get ho-oh and lugia! yipee
Im prettly sure once you own all 151 Pokemon you'll receive some sort of diploma by Professor Oak
u win the grand monologue and all your Pokemon go to lvl 99. actually i think professor oak gives u a diploma that's what happens in all the other games.