Cody starts the game by helping Lisa and a kid who's being bullied, saving them from Bisco's thugs.
Rescuing Lisa from Bisco, and later her own father. She cheers you on with every floor of his tower you destroy.
If you refuse to give up Dosbot without a fight, you get beat up. The girl that gave Dosbot to you is sorry it happened and apologizes to you.
Underwater creatures are seen throughout the game, and you can help one that got separated from his family find them again.
After you beat the game, Princess Darcy is still imprisoned in the cursed mirror. When you finally get the Teardrop of Morris and save her, she and Prince Tail are extremely grateful and give you special software as a reward.
Meta example related to this: A Gameshark code exists that can place a Teardrop of Morris in the player's inventory. Even an emulated rom of the game can allow the player to save her now.
The end of the alien storyline in the second game. Tataki realizes that, alien or not, he really does love Miho. She reciprocates his feelings, and he promises to find her on the moon.
Saving Mr. Waffle's company, which brings him out of financial ruin and lets everyone enjoy his games again.