The City of St. John's Police Headquarters in the show is actually the Bruneau Centre for Research located on Memorial University of Newfoundland and Labrador's St. John's campus. Staff and students would see police related signage pop-up ahead of filming on their way to work/class, and the university would email notices to "not be alarmed by the appearance of police presence".
Based on the Austrian show Kommissar Rex.
The series was filmed in the Canadian province of Newfoundland and Labrador, after which two breeds of dog were named. Rex, on the other hand, is a German Shepherd.
Meghan Ory the wife of John Reardon (Charlie Hudson) appeared as a guest star on the show as Deputy chief of SJPD . Hudson & Rex season 4 Episode 5
Thanks to Newfoundland and Labrador's public health measures and ability to keep COVID-19 cases low in 2020, production on season 3 was largely uninterrupted. Production was halted for two weeks after a crew member tested positive, but no ensuing outbreak was reported.