Ubisoft Milan’s creative director Davide Soliani who worked on Mario + Rabbids Kingdom Battle showed off a paper prototype used for development of the game. This was most likely in the phase of bringing the concept to life from paper to digital. Here’s what he had to say:
Our first prototype ever, a paper game made of modular pieces, tons of printed and glued together cubes, dices, rulers and patience.
This kind of thing reminds me of the early days of NES and SNES where Mario creator Shigeru Miyamoto would plan out levels for Mario with the development team at Nintendo using sheets of graph paper taped together to construct levels before implementing them into the games. Even though technology has created tools for easier developing, it seems not all traditions are lost!