Jeff Fowler and Tyson Hesse, director and artist, respectively, for Sonic the Hedgehog 3, participated in the Sonic Revolution online expo livestreams. During the course of their presentation Fowler said the following about Keanu’s approach to Shadow:
It’s so awesome that we got Keanu Reeves to voice the character, and he was so fantastic to work with. I think he thinks the character is awesome. I think he definitely understood what we were going for and was very excited to kinda do his version of it, but he, like all the cast, really wants to get it right, really cares.
He would give us so many different versions of line readings and just wanna keep going. He was not just sort of showing up and just reading the script into a microphone. Like he really wanted to create a very fan-faithful version of the character. He did research. In our first meeting, he very clearly had gone and done his homework, which was awesome.
And so, I just can’t say enough wonderful things about Keanu and what he brought to the character, and just the experience of making this movie.
Source: Sonic Stadium