What happens when you get all 150 Pokemon in fire red version?

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