>>212395262No, it was incredibly careful threading of needles by Spielberg and Zemeckis, and a miracle that it happened at all. Getting Disney and Warner Bros to cooperate was no mean feat.
For instance, Bugs and Mickey, because they're the respective mascots and both were extra protective, could ONLY appear in the same scene, and they had to have precisely the same amount of screentime to the frame. In this scene, Mickey enters from the top a frame before Bugs does, and at the end of the scene, Bugs exits the scene second, a frame after Mickey.