Barry Morse (Professor Victor Bergman) made attempts to rejoin the series while pre-production for season two was underway, but incoming producer Fred Freiberger was against him returning, preferring a younger cast. An explanation of his absence was included in the episode The Metamorph (1976), but ended up being edited out of the finished cut. Dialogue indicated he had been killed due to a faulty spacesuit.
The TV monitor built into the 'comlock' unit each Alphan carried wasn't a clever special effect but a real miniature tv set available in the early 1970s (Panasonic TR-001) that had a 1.5 inch black and white screen. The props department cannibalised the model and rehoused it into a more appropriately futuristic casing. When we see the screen in use it is always held from a particular angle to hide the power and live video feed cables running into it. The numeric buttons on the side probably came off an early electronic calculator such as a Craig .
Special effects supervisor Brian Johnson was asked to helm the special effects for Star Wars: Episode IV - A New Hope (1977), but his involvement with this series took priority. While helming the special effects for Alien (1979), Johnson was asked to take charge of the effects for Star Wars: Episode V - The Empire Strikes Back (1980), so he left the effects duties for Alien (1979) with his assistant on the project, Nick Allder, who had also been his main special effects assistant on this show, then moved on to work with the effects crew on "Empire". Johnson and Allder ended up sharing an Oscar for Special Effects for Alien (1979), then Johnson shared a Special Achievement Award for Special Visual Effects on Star Wars: Episode V - The Empire Strikes Back (1980). Johnson would later go on to helm the post-production visual effects on Aliens (1986), in which he would end up sharing a BAFTA Film Award.
In order to familiarize himself with the series, Season Two Script Editor Fred Freiberger apparently viewed just eight of the first season's twenty-four episodes. He critiqued each one, lauding season one's production values, but regarded the scripts as slow, dull, and humorless; the characters one-dimensional; and the plots disorderly. Head of ITC, Lew Grade, had suddenly just decided to cancel production of the show's second season, so Freiberger met with him, showing him his reviews of those eight episodes, with ideas of how to improve the series. Freddie made such an impression that Grade reversed his decision and Freiberger was given the additional role of Producer. However, his "improvements" turned out to be highly questionable by the cast and crew, as well as most of the audience.
At the time, this was the most expensive series ever produced for British television, or for syndication.