The movie was not a throwaway "what-if" story. It was official canon for both series. It provided critical backstory for Generator Rex regarding the origin of Alpha and the Nanite Project. For Ben 10 fans, it gave Shocksquatch his official debut before he appeared in Ben 10: Omniverse . The Legacy of the Crossover
Here’s a concise draft logline and short synopsis for a Ben 10 × Generator Rex: Heroes United movie. ben 10 generator rex heroes united movie
Like all great superhero team-ups, Ben and Rex don't get along immediately. After a misunderstanding, they fight——before realizing they are on the same side. The movie was not a throwaway "what-if" story