When it was first introduced, the Star Winning Gundam created a great big hooha both in the anime and in the real world, with multiple theories sprouting of the new Winning Road, the waist- and appendage-like assemblies that comprised its strangely-large backpack as well as what seems to be a V-Fin upon a V-Fin. With the conclusion of episode 18 (and "leaks" of the box art prior), all these fantastic theories were finally put to rest when we finally saw the Star Winning Gundam's Real Mode in action, and even if it was a little tame as compared to the antics of Sekai Kamiki, it was still wondrous to behold.
Many builders thought that this SD to HG transformation gimmick is new, some brilliant new maneuver to sell kits thought up by the famous (infamous) Bandai Hobby Division. However, this class of SD kits has been around since 1995, in the form of a series of BB Senshi Musha kits that were able to shed their SD facades to become 1/144-scale mushafied versions of UC mobile suits. Therefore, the technology behind the Star Winning's primary gimmick isn't new, it merely is a resurrection of 20-year-old model kit engineering. Nevertheless, the transformation system in the Star Winning has received substantial refinement and upgrade to close the 20-year gap, but fundamental flaws still mar the articulation and poseability of an otherwise beautiful and very unique model kit.
UPDATE - Star Winning with Haganemaru Katana