Maria’s Illness
In the games, Gerald was deeply invested in finding the key to immortality because his granddaughter, Maria Robotnik, had a terminal illness called Neuro-Immune Deficiency Syndrome. This led to the creation of Shadow and his prototype called the Biolizard, immortal creatures made with the hope that they could help facilitate similar breakthroughs for humanity. However, Maria seems to be a perfectly healthy kid in Sonic 3. I suppose, since Gerald isn’t creating Shadow in this timeline, there was no need to include her sickness as a motivator for his research. The sibling-like relationship between Maria and Shadow still hits many of the same notes, however. In both continuities, the two become inseparable friends that bond even as Shadow is being subject to experiments every day. Eventually, Maria’s death at the hands of GUN agents leads Shadow to try to destroy the world in both the games and the movies, but she lived her life as a healthy young girl in the films.
