Barry Morse was left out of the show's second season due to Fred Freiberger being intent on discouraging Morse from returning - using his idiom "Science fiction needs young faces." Freiberger plotted against him from the start; first by offering him a salary much lower than the first series, then ignoring his phone calls while Morse and his agent were attempting to negotiate the offer. Martin Landau and Barbara Bain lobbied for Morse's return, but it fell on deaf ears. Gerry Anderson steered clear of these events, allowing Freiberger to run the show. Although he gave himself the title of Executive Producer, Anderson remained on the sidelines during production, simply being present just to collect the paycheck while the Americans ran the show (and some believing that he was still bitter over his and Sylvia Anderson's split, allowing Season One's cast to be let go out of spite, as Sylvia had a hand in their casting, apart from the two leads). Landau was disappointed with Morse's departure, believing the show wouldn't be the same without the Victor Bergman character. An explanation of his absence was filmed for this episode but was edited out of both the syndicated version and the DVD. Dialog indicated he had died due to a faulty spacesuit. In order to save face, an embittered Morse later stated in interviews that it had been his idea not to rejoin the series after Season One ended; these interviews invariably conducted with Morse displaying a negative attitude toward the show (although praising his former co-stars).
Maya's eyebrows were designed with the hope of being as distinctively popular as the ears of Spock, the half-human Vulcan science officer in the science fiction series Star Trek (1966), a show of which Catherine Schell had been a big fan.
This episode was originally written by Johnny Byrne in September 1975 with the Season One format (therefore without Maya), titled "The Biological Soul", involving Mentor living alone on the planet with his Overseers and alien slaves. When Fred Freiberger took over in the dual role of Producer and Script Editor in December 1975 (after rescuing the series from cancellation by coming up with the character of Maya) - retitling it "The Biological Computer" - he inserted Maya into the script and removed most of Season One's characters, apparently underestimating the intelligence of the show's audience, convinced that they didn't care about the supporting players and wouldn't even notice their disappearance (at the SpaceCon II convention in 1979 in Pittsburg, attended by Prentis Hancock, Anton Phillips, and Nick Tate, Hancock stated that he still had no idea why he hadn't been invited back to the series for Season Two). This original Freiberger version of the episode had the Tony Verdeschi character named Simon Hayes, the Chief Eagle pilot named Mark MacInlock (replacing Alan Carter, as at this point Freiberger had no intention of re-signing Tate to the series), the events beginning 108 days after leaving Earth, and Eagle One surveying the planet for the mineral "tiranium" (which would've been consistent with Catacombs of the Moon (1976)). The script was subsequently tweaked (and renamed again in honor of Maya herself).
While Gerry Anderson and new Script Editor Fred Freiberger were beginning pre-production of the show's second season in November 1975, dipping ratings of Season One airing in America caused head of ITC Lew Grade to cancel production of Space: 1999's second season (Grade had always been reluctant to renew any TV series he'd been financing that hadn't been picked up by a major American network, preferring to keep moving onto new projects with the hope that one of the three American networks would be interested in it). At this point, Anderson and Freiberger storyboarded two brand new proposed live-action series; "Rescue 4" (aka "Intergalactic Rescue"), which combined the concepts of the previous Anderson Supermarionation series' Supercar (1961) and Thunderbirds (1965), offering it to NBC, which turned it down; the second creation was offered to CBS, titled "Starcruiser", aimed at children (inspired by the Gerry Anderson-produced series pilot recently seen on NBC in November 1975 titled "The Day After Tomorrow" (aka "Into Infinity"), which never made it beyond the pilot episode), but CBS turned it down. Grade was then introduced to Freiberger's concept of the new character Maya, which helped convince him to green-light Space: 1999's second season; Script Editor Freiberger was then given the additional role of Producer.
To introduce the new season, three versions of a promotional TV ad were put together for each of the US stations carrying the show to air. The most-played one was hosted by Martin Landau and Barbara Bain (after introducing themselves - Bain: "The new season of Space: 1999 is more exciting than ever." Landau: "We have Catherine Schell as Maya - the Wonder Woman of Science Fiction". Bain: "And lots more - watch". A clip of Maya's transformations from the climax of "The Metamorph" followed, ending with Bain: "The new Space: 1999 - bigger, better, more exciting than ever" - even though the sets are all blatantly smaller); Schell hosted one by herself (in full Maya makeup, as Bain had forced a clause in Schell's contract that forbade her to ever appear without her Maya look); Tony Anholt and Nick Tate hosted the third.