User blog comment:Kogath/Monster Hunter 4 Ultimate for the Nintendo 3DS/@comment-21860237-20140422020844/@comment-184612-20140422133642

Actually Crimson wasn't shown ever. Hackers stumbled upon its materials in the game code and then it showed up when trying to get Fatalis to spawn in the Great Forest. We didn't officially get the monster until quite awhile after release, and we never would've known about it being in the game without hackers taking it apart.