One of David Kemper's proposed alternate titles for this episode was "Skreeth on Earth, Goodwill to All Men."
The fight between Crichton, Aeryn and the Skreeth was originally going to finish with the house being totally wrecked. The production team would have used a real building scheduled for demolition and finished the job.
David Franklin admits that he didn't know exactly what accent he would use when he was possessed by the Skreeth until he began shooting the scene with Rebecca Riggs.
According to the script, "Terra Firma" starts during the autumn of 2003 and finishes on Christmas Eve.
Ben Browder nominates "Terra Firma" as on of his favorite episodes of the fourth season, and of the whole series, because it took the risk of taking Crichton back to Earth for real.
The exterior shots of the crew's temporary home were filmed at Abbotsford, a small town just down the Parramatta River from the Farscape studios at Homebush.
The line "Merry Frelling Christmas" was an ad lib by Claudia Black on the set at the end of shooting of the fight sequence.
The Skreeth was deliberately colored green by Jim Henson's Creature Shop as a quiet homage to Dr. Seuss's killjoy The Grinch.