When Number 6 asks Mrs Butterworth 'What's the date?' She replies Saturday March 18th, to which he replies 'Tomorrow is my birthday' March 19th is actually Patrick McGoohan's real birthday.
Patrick Cargill, who plays Thorpe, later appears as Number Two in Hammer Into Anvil (1967). It is left ambiguous as to whether or not it is the same character.
The first character to utter a line of dialogue speaks at 15 minutes 25 seconds. Number Six doesn't speak until 22:50.
About his car, Number 6 tells Mrs Butterworth, "I know every nut and bolt and cog; I built it with my own hands." The car is a Lotus Seven, which was originally available as a kit. Under UK tax law of the time, purchases of kit cars were taxed at a lower rate than assembled cars, but in order to get the lower tax rate, the kits were not allowed to include any assembly instructions.
The opening sequence does not show Number Two, nor does the voice match that of Number Two. Number 2's opening spiel is voiced by Robert Rietty as was the case for 6 of the other episodes.