Sid Stands for Disney
Out of all of our Disney fan theories, this one is definitely the most meta. Those familiar with Disney history know that animator and director John Lasseter was fired from the company and ultimately ended up working for Pixar. So, fans speculate that Lasseter named Toy Story’s villain after his former employer. “Sidney” is an anagram of “Disney,” so this theory suggests that Lasseter named snot-nosed kid Sid from Toy Story after the major studio. It’s an animation anagram burn.