With the real Arthur the dog living until December 2020, six full years passed since the race that brought them together. Mikael Lindnord (the real life racer) has not adopted another dog since Arthur's passing. Furthermore, Arthur's death occurred just weeks before Arthur the King began filming.
Mark Wahlberg tore his knee on the first day of shooting and implemented the pain of his injury into his performance.
Even though shot & set in Dominican Republic, the actual real life events occurred in Ecuador.
It is based on the 2016 non-fiction book Arthur - The Dog Who Crossed the Jungle to Find a Home.
The Arthur Foundation was founded to help dogs around the world receive better care. This included supporting the LOBA law in Ecuador (Organic Law of Animal Welfare Ley Organica de Bienestar Animal), which went into effect in April 2018.