Actor Allusion: In a Comic Relief episode Uncle Albert mentions how nice it would be to walk through a door into the 1940s, which Rodney dismisses as stupid. Raquel then goes to bed and Del says "Goodnight Sweetheart.". Del then remarks that he is not a chief inspector.
This was also done the other way around—in Goodnight Sweetheart Gary (played by Nicholas Lyndhurst) is about to lean back and fall through an open bar door like Del Boy famously did, but notices in time and gives an Aside Glance wink to the audience—accompanied by uproarious laughter that must seem inexplicable and random to anyone unfamiliar with the Only Fools scene in question.
Hey, It's That Guy!: Jim Broadbent plays Slater. Less significantly, Lennox Gilbey from "The Longest Night" was played by Vas Blackwood, aka Rory Breaker in Lock, Stock & Two Smoking Barrels. Eagle-eyed viewers might also spot David Thewlis as one of the members of the band in the fourth season episode "It's Only Rock and Roll".
The same applies to the original version of "A Royal Flush," which is unavailable on any home video format (the VHS release had about a minute of footage removed, and the DVD release removed nearly ten minutes of footage and added a laugh track). However, the original cut still appears from time to time on UKTV Gold and other such channels, so it's not too hard to find decent quality versions of it.
In a straight version, several mini-episodes such as Christmas Trees, Licensed to Drill and the Comic Relief Special have never been released on VHS or DVDs.
Jim Broadbent was John Sullivan's original choice for the role of Del. While Broadbent turned down the role, he did later make three guest appearances in the show as DCI Roy Slater.
Enn Reitel, Robin Nedwell, and Billy Murray were also considered possible candidates for the role of Del, before it went to David Jason.
John Sullivan intended for Chas & Dave to sing the series' theme song due to the success from their "Rockney" style of music (a mixture of rock 'n roll and cockney). However, they were unavailable having just recorded their hit single "Ain't No Pleasing You", so Sullivan was persuaded by Ray Butt to sing the song himself, which he did.
In 1986, David Jason told John Sullivan at a dinner that he wanted to leave the show and further his career elsewhere, so the fifth series finale "Who Wants to Be a Millionaire" was written as the final OFAH episode, and would have seen Del leaving England with his friend Jumbo Mills to run a car business in Australia. A spin-off entitled Hot-Rod was planned, which would've been all about Rodney running Trotters Independent Traders with Mickey Pearce. However, Jason changed his mind and decided to stay on, and Sullivan rewrote the ending to show Del rejecting Jumbo's offer.
In the first chapter of the early 2000s Christmas trilogy, "If They Could See Us Now" (2001), The BBC wanted to get the rights from ITV to use the actual Who Wants to Be a Millionaire? gameshow with a special guest appearance from Chris Tarrant, but ITV refused because a plot point was that Del gave a correct answer and the quizmaster said it was wrong due to an error. They ended up with a blatant expy called Goldrush, hosted by Jonathan Ross.