There’s a unique problem that the producers of anime-to-live-action adaptations face. Even if the casting director can gather a group of actors that look just like the source material’s human characters, what do you do about the non-human characters?
Using practical effects and animatronics for all those loveable robot companions and magical creatures limits the variety of movements they can handle and the angles you can film from. On the other hand, using post-production CG effects leaves the actors in the difficult position of having to perform while imagining costars that aren’t really there, which often leads to less-than-convincing results.
Maybe that’s why an upcoming Chinese live-action version of Doraemon has decided to go with the obvious solution and just use a real cat for the titular feline robot.