Smash 3C is heavily inspired by Smash 3. Hence the name.
 

Smash 3 didn't make alternate costumes, sans Dr. Mario, but they did make all of the core Project M and Brawl characters as well as the HUD. While Smash 3C may offer alternative options like Brawl models and custom versions, Smash 3 has all of the original characters, and is essential to anyone who wants to create a pack or build with the Smash 3 and 3C aesthetic.

Smash 3's goal was to be a visual overhaul of Brawl and Project M with the artstyle of Super Smash Bros. for Nintendo 3DS & Wii U. It spawned as Taiko decided to change his project from a "Smash 4 Mario", to a project called "New Smash". As for Shun, he had just finished his "Vibrant Brawl" project and felt he could do something bigger. After approaching Taiko, the two decided that the project would be called Smash 3. On June 31st 2016, Smash 3 released every single character from Brawl and Project M, and we've provided links to everything, to make it easier for users to personalize builds. These will not be updated.