Commander Ray Neptune is joined by robot Circuit, scientist Doctor Asteroid and the mysterious "space maiden" Athena, who only communicates via telepathy.

[2] The series was created by Stephen La Rivière and Andrew T. Smith and their production team during the COVID-19 pandemic in the United Kingdom - finding themselves unable to continue planned studio production work, the film-makers created the series in a flat with puppets, props and materials from earlier productions such as Filmed in Supermarionation, Thunderbirds: The Anniversary Episodes and the Endeavour episode "Apollo".

[5] The authentic 1960s feel of the production was discussed by Samira Ahmed with La Rivière on BBC Radio 4's Front Row on 19 May.

[6] Ahmed later lent her voice to a news reporter character, Juliette Destiny, for the 2020 Christmas episode.

The series' broadcast on Japanese television was preceded by theatrical screenings of Nebula-75's first episode, shown in cinemas across the country alongside three special anniversary editions of Thunderbirds produced for that series' 50th anniversary by members of the same production team.