To see the other ''special'' ending to the game, unlock Mr. Satan and get him to Level 50. Then, go to West City and break down the Level 50 door to ZZTV and you'll see a different ending to the game.
While playing as Vegeta charge up the big bang attack as soon as you start charging pause the game and Let go of the charge button then unpause the game and it will charge automatically
After you find all 7 Nameks take them home and Cooler will be waiting to fight you. The dialogue before the battle will be different if you use Trunks or Goku.
In the Capsule Corparation, go to Level 2. There, talk to Mrs. Briefs. She will give you a cookie. Continue talking to her, and she will never stop giving you cookies. These restore a small amount of HP every time you eat one.
To get Gohan's Trophy , simply get to Level 50 with Gohan then go to the ''50'' gate outside Gingertown to collect the trophy.