In one episode, the phrase "mating season" is used in a scientific context.

Both "The Robot Revolution" and "The Buried Spaceship" feature Slim expressing his love to Marla, Raeburn's secretary, who is also Venusian.

As the programme dates back to 1962, its ideology often reflects sexist attitudes to women at the time. For instance, "For a woman she doesn't talk much!" (several episodes), "Looking lonely as ever and talking nonsense just about makes her a normal woman!" ("Destruction by Sound"), etc. Modern viewers may be offended by this.

Mild violence.

Towards the end of "The Swamps of Jupiter", there is a fist fight between three men. However, this is extremely brief, and there is no blood or gore.

A robot bashes Colonel Raeburn in the head, knocking him unconscious ("The Robot Revolution").

Extraterrestrial animals are killed on-screen in certain episodes.

Explosions are occasional. They are not as realistic as those on "Thunderbirds".

No profanity, although mild name-calling is occasional ("stupid", etc.).

Characters are occasionally seen smoking. For example, at the beginning of "The Jitter Waves", Colonel Raeburn smokes a pipe.

In "Secret Formula", a criminal is given a drug which forces him to admit to murder.

Characters in danger or facing potential death may unsettle young children.