James Marsden says Sonic's stand-in props while filming the movie were a tennis ball, blue beanbag, and a stuffed Sonic

Many of the actors in the Sonic the Hedgehog movie had to interact with inanimate objects during their scenes with Sonic. Actor James Marsden had more scenes with Sonic than any other person on the film, which meant he had to do a lot of one-way acting. In an interview with Comicbook.com, Marsden reveals what he had to play off of when filming Sonic scenes.

So it was three different versions of my co-star on set, which was either a tennis ball attached to a tripod or a blue stuffed animal Sonic that was roughly the same size and dimensions as what our guy would be. And then there was a blue beanbag if I was ever carrying him, because it just sold the weight of me holding something that had weight to it. And that was kind of it. Other than that, I just had to use my imagination and would get Ben Schwartz on the phone whenever I had an idea for a scene or asked him how he was thinking about playing it. And we would kind of maybe run it in a scene if we were on the phone, and I would just sort of get the rhythms of it. And we'd do it 10 different ways, and then move on.