I am a sucker for character growth, especially when the story takes place over a long amount of time, so of course it's always nice seeing the characters not only grow as a person, but also change their clothes from time to time to reflect that a little bit! 
The first outfits for my project's characters are more easy and simple, some don't even change much besides some pieces here and there. For most of the crossover characters, they also got different/new outfits, but I plan on letting them show up in some of their iconic ones every now and then after Part I. Also, power-ups; those will show up and change over time, lots of training and character development. Like, going from simple to more detailed armor/weapons, the stronger the power-up is :3