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Mauville Game Corner's Service Day

After you beat the Elite Four, the TV everywhere in Hoemn(Pokemon Ruby/Sapphire/Emerald) will sometimes tell you that the Game Corner's Serive Day is coming in 0-3 days. On the service day, your odds of winning at the Game Corner is increased.

Latios/Latias/Suicune/Raikou/Entei

Getting Latios/Latias/Suicune/Raikou/Entei in Pokemon Ruby/Sapphire/Emerald/LeafGreen/FireRed is not completely random. After about 20 hours after beating the Elite Four, Latios/Latias/Suicune/Raikou/Entei will appear. It does not depend on how many Pokemon you see. I once saw only 10 Pokemon in the wild before catching Latias in Pokemon Emerald. Another time, I saw about 50 Pokemon in the wild before catching my Suicune in Pokemon FireRed.

Getting 50% off Vitamins

After you beat the Elite Four, the TV everywhere in Hoemn will sometimes tell you that the Energy Guru in Slateport City is going to do something important on an important day and that day is coming in 0-3 days. On that day, you will get 50% off all Vitamins. But remember, this will only last for one day!