Have you noticed that if you try to fly around as super sayan you'll turn back into normal? Well after Goten and Trunks first fuse into Gotenks and fight fat Buu, they are told they have to take a nap, but instead you can fly outside and gain exp, get items, ect. if you turn super sayan and fly out the window, you’ll stay super sayan, its a bit glitchy though. This cheat can be used throughout the whole game and with every character.