Cast changes during the series included:
- Computer expert Ouma (in Breakaway only) was replaced by Kano for the remainder of Year 1
- During The Infernal Machine, Paul Morrow disappeared (with an explanation) and was replaced by Winters.
- After Year 1, several characters disappeared without explanation: Victor Bergman, Paul Morrow and David Kano.
- For Year 2, Tony Verdeschi appeared without explanation
- During the course of Year 2, almost all characters would appear and disappear in certain episodes without explanation (this was due to double-up filming and supporting cast being contracted on an episode by episode basis). This included Helena Russell, Maya and Tony Verdeschi (an explanation was always given for Koenig's non-appearance).
- During episodes of Year 2, when Sandra Benes was absent she was replaced by Yasko. Towards the end of the series she was replaced by Alibe.
- During episodes of Year 2, when Alan Carter was absent he was replaced by Bill Fraser.
- After the initial episodes of Year 2, Bob Mathias disappeared and was replaced by Ben Vincent. Towards the end of the series, Ben Vincent disappeared and was replaced by Ed Spencer
Copyright Martin Willey