Initially, Keaton auditioned for Shiro, Keith, and Lance, but did not get any roles until he was called back a second time sixth months later after the first voice actor for Shiro did not fit. Keaton did not believe he would not be replaced, even after recording some episodes to see how his voice meshed with the rest of the cast, because no one gave him a clear answer on whether or not he earned the role of voicing Shiro. It was not until they were doing press releases that Keaton felt secured on the series cast.
Keaton is a fan of Defender of the Universe, having watched it as a kid and rewatched it as an adult, and loves how Legendary Defender pays homage to both the original Voltron show and Beast King GoLion.
Keaton feels he can connect with Shiro thanks to being a father and sharing the responsibility of looking out for the life of another being, because Shiro must act as leader of the Paladins and protect the lives of Team Voltron. Growing older and having kids has made Keaton gain patience that he feels he can mirror in Shiro, and he thinks of Shiro's method of helping the team work together rather than force anyone to cooperate or stay reflects the way Keaton "leads" his family.
- Keaton has a Black Lion toy from childhood; it is the only Lion from that generation he has and ever got to play with, so the Black Lion is his favorite.
- Keaton also has a Gladiator Voltron toy that was given to him by his father, who received it from one of his students while teaching English as second language.
- Keaton acknowledges Shiro's fan nickname of "Space Dad" and has adopted it as his own moniker.
- Keaton possesses several other Legendary Defender merchandise including a Galaxy Garrison coffee mug and a fan-created Shiro varsity jacket.
- His favorite episodes are Space Mall and Crystal Venom, the latter because it is the first time viewers see Shiro start to break down.
- Keaton has a pet dog named Sir Chauncimer or "Chaunce(y)".
- According to his official bio: "In his spare time, Josh, a former lead singer of boyband No Authority enjoys singing, writing and producing music, tinkering with cars and all things mechanical and electronic, and spending time with his family."
- For Christmas Eve 2016, Keaton released a video parodying A Visit from St. Nicholas with Coran as Santa Claus.
- For his 39th birthday, Keaton released a video of him singing about Shiro with a song parodying Your're Welcome from Moana; the video features himself, Kimberly Brooks, Bex Taylor-Klaus, Neil Kaplan, and AJ LoCascio.