Dawson Casting: Inverted with Clive Dunn (who was 47 when the series began) playing the septuagenarian Corporal Jones. Played straight with Ian Lavender, who was 22 at the start of the series and playing the 17 to 18-year-old Frank Pike, and 31 when the series ended while Pike had not aged.
Executive Meddling: Worried that the sitcom would be criticised for ridiculing the Home Guard, the BBC insisted on adding an opening scene to the first episode. It shows Mainwaring, in 1968, giving a speech at a formal dinner in which he explains how he and his men "backed Britain" in 1940. The scene lasts a minute-and-a-half, has no jokes whatsoever, and has no relation to the rest of the story. Had it been broadcast in an age when there were more than just three TV channels in the UK, it could well have killed the series before it even began, and co-writer Jimmy Perry suspected it was responsible for the overwhelmingly negative feedback from the test audience who got a preview screening of the first episode.
Barbara Windsor appears in a Series One episode as a showgirl who performs a trick shooting act, roped in by the platoon to disguise herself as a Home Guard member and help them win a marksmanship contest.
In the same episode, show writer Jimmy Perry appeared in a small role as a stage comedian; he had originally wanted to play Walker but decided against it in case it caused friction with the rest of the cast.
Nigel Hawthorne appears in a brief role in the first episode of Series 3, playing a man whose bike gets commandeered by the squad.
The Season Three episode This Bullet's Not For Firing guest stars Michel Knowles, who played Captian Ashwood in Perry & Croft's It Ain't Half Hot Mum, as a visiting captain who attends the court of inquiry.
Also from It Ain't Half Hot Mum, Don Estelle, who played Lofty, is the man from Pickfords in the season three episode Big Guns.
Peter Butterworth guest stars in the season 8 episode The Face On The Poster as a printing clark.
Missing Episode: Most of the second season. Two episodes were subsequently recovered and remastered. One of the colour episodes only survived in black and white; it has since been recolourized, though the colour version has not yet been released on DVD.
The Other Darrin: Mrs Pike was recast for The Movie because the studio felt the original actress wasn't high-profile enough. During the live stage show, several parts were recast while the TV actors had other commitments.
Real-Life Relative: Pike's occasional girlfriend Ivy was played by Ian Lavender's wife in one of her appearances, the episode "My British Buddy"
Arthur Lowe's wife, Joan Cooper, took over the role of Godfrey's sister Dolly towards the end of the show's run and played other guest roles during the course of the series.
Word of God: Ian Lavender waited until very late in the show's run to ask Jimmy Perry if Pike really was Wilson's son. Perry replied that as "of course he was!". David Croft also confirmed it as fact in interviews.