If Kris gets KO'd in the Sweet Cap'n Cakes battle, Susie and Ralsei will instantly begin to learn S-Action and R-Action. Kris will also still be KO'd in the ending dance scene.
It is possible for Susie to die in the battle with Lancer at Card Castle if you get her HP low enough and play through all of the Forest without ever saving. (Saving would cause Susie's HP to replenish, even when she's not in the party.)
If you defeat Spamton NEO with a full inventory of Weapons/Armor (depending on if he's beaten violently or spared) the cutscene afterwards will be extended with new dialogue.