This series is actually a reboot of the original Jethroverse series (produced from 2016-17), which was in itself a spinoff of a web series of "The Four Squares of Justice." Many cast members return from the original, including Brennen Savery, Tim Wood, Rowan Wood and Lir Wood.
Even though filming officially began on December 2, 2017, scenes with stars Brennen Savery and John Shortis were filmed a week earlier, on November 26. However, this scene was ultimately scrapped and replaced with an alternatively-filmed sequence.
A scene in episode 4 involving a funeral home originally starred prolific author Bernard Cornwell as the funeral director, but he was unavailable for the role, and so both Paul Schuyler and Lou Maloof were offered the role. Maloof ended up filming the scene on December 9, 2017.
The role of Brooke, Jethro's girlfriend in Season 2 in The Jethroverse (2018), is played by Julia Holcomb, Brennen Savery's real life ex-girlfriend (as of January 20, 2019).
According to The Jethroverse (2018)'s star, Brennen Savery, the original "Jethroverse" was rebooted because the actress who was going to play Jethro's girlfriend in Season 3 exited the project due to other commitments.