Ultimate Chicken Horse started as a game that Kyler, Alex and Richard (our co-foudners) made for a game jam. The game jam had three themes: Modular, Phrase, and "L'ultime ____".
Initially, the modular aspect was going to be this idea of typing words which became items, kind of like Scribblenauts, but where the letters themselves morphed into objects. Then somehow that led to the simpler concept of a player creating a level, which another player then had to go through.
We settled on making a 2D game, and Kyler came up with the characters of Chicken and Horse. For the controls and physics, Super Meat Boy was our main inspiration.
Initially, the way scoring was done was that you received a letter if you failed, in the way that people play H-O-R-S-E in basketball or S-K-A-T-E with skateboarding. The game is meant to be the ultimate game of HORSE, but also the ultimate game of Chicken (where people dare each other to do something stupid and dangerous things until someone forfeits... or gets hurt).
After the game jam was done, we showed the game at a local game dev meetup and gathered feedback, and then put some more polish into it to show it at a bigger local game pitching event. This became the version of the game that we shared as a demo for our Kickstarter campaign, and the core design of the final product.