Big Lipped Alligator Moment: Rodney's nightmare at the beginning of the first chapter of the 1996 Christmas trilogy, "Heroes and Villains", in which a grown-up Damien not only runs Trotters Independent Traders, but also rules the western world in the year 2026, declaring war on other countries. While Del Boy, Lord of Peckham, and Raquel live a luxurious life in Trotter Towers, Rodney himself is reduced to being an old messenger, Cassandra is a maid after Damien took over her bank and fired her, and Uncle Albert's body has been preserved, repeating his trademark phrase on a constant loop. As Rodney berates Damien for ruining everything, Del wakes him up.
Casting Gag: Douglas Hodge, the then-husband of Tessa Peake-Jones, who plays Raquel, was cast as the grown-up Damien in Rodney's dream in "Heroes and Villains".
Fanon Discontinuity: Many fans ignore the 2001-03 Christmas trilogy because it completely undid the 'perfect' ending of the original finale; the 1996 Christmas trilogy, where the Trotters at last achieve their dream of becoming millionaires and walk off into a glowing sunset... apparently only for Del to lose it all on the stock markets. (Though they do gain a sizeable portion of it back through Uncle Albert's will in the final, final episode.)
Despite this, the very last episode "Sleepless in Peckham" is considered quite touching, especially when Rodney and Cassandra finally have their daughter, Joan Trotter Jr.
One detail that needs highlighting is the end line. At the close of the first 'last episode' Del declares, "This time next year, we could be billionaires," a superb twist on his defining catchphrase. After 2003, the final line would always be, "D'you know Rodney? That's a bloody good idea." Which doesn't quite have that same ring to it.
Perhaps a real-world case of Be Careful What You Wish For. Its status as Britain's most popular sitcom meant writer John Sullivan had been asked about a return almost constantly. And to give him some credit, he was trying to keep a sense of perspective. The wider context of the 'billionaires' gag was Del's enthusiasm for investing in the futures market - which did undergo a genuine slump not long after the episode originally aired.
Interestingly, Sullivan originally wanted the sunset ending to be done as a cartoon, indicating that the characters were no longer in the real world and would not be coming back, but this was rejected.
In the 1983 Christmas special "Thicker Than Water", Reg Trotter returns, and comes close to convincing his sons that he isn't really Del's father. Much later, the 1987 and 2003 Christmas specials "The Frog's Legacy" and "Sleepless in Peckham" would suggest that Rodney wasn't Reg's son (although "Thicker Than Water" already had a pretty strong implication of that itself - or at least that Del had reason to have always thought it was a possibility, yet he didn't know the truth until a drunk Albert told him).
In the episode with the seance, Trigger says that the figure being described by the spirit medium 'sounds like Jimmy Savile', when it was in fact Del and Rodney's mum. They were not impressed by the comparison even then, and this was long before the truth about Jimmy Savile became known.
In an earlier episode, Del tells Albert that some of his ex-girlfriends are married, while a couple are dead. David Jason's long-term partner Myfanwy Talog died in 1995, and the line is sometimes excised from repeats, possibly for reasons of sensitivity.
In "It Never Rains...", Grandad mentions a friend called Nobby Clarke. Kenneth MacDonald, who played Mike from "Who's a Pretty Boy?" to "Time On Our Hands", played a character by that name in It Ain't Half Hot Mum.
In the 1992 Christmas special "Mother Nature's Son", the Trotters attempt to pass off tap water as "Peckham Spring Water" — it glows in the dark due to dangerous contaminants. Coca-Cola would proceed to do this when it launched Dasani in the UK. That and the discovery of carcinogens led the product being pulled. When Dasani was found to be just filtered mains water, it got nicknamed "Sidcup Spring" after this episode and the location of the Dasani bottling plant. Which just adds to the parallels with the episode, since Del managed to pollute the 'Peckham Spring' water with some chemical dumped in the reservoir (that caused the water to literally glow in the dark).
In her initial appearance, Raquel mentions that until that point her career highlight had been a small role in an episode of Doctor Who — which was intended to show how spectacularly unsuccessful she had been as an actress, since the show's ratings and reputation were a complete joke by that point, and it would be cancelled just under a year later. Exactly 25 years later the actress who played Raquel, Tessa-Peake Jones appeared in Matt Smith's final episode as the Doctor, with the show's reputation pretty much the opposite of what it was when Raquel first appeared.
Moral Event Horizon: When Slater is first introduced, it becomes clear that he is incredibly petty and a bully even to his fellow police officers. When Del, Rodney and Granddad refuse to grass on whoever gave them a stolen microwave, he threatens Del, with planting drugs on Rodney, and promises that while they do their time in prison, Granddad will be left alone on the estate. This is when you realise just how loathsomely corrupt this man is.
In Reg Trotter's sole appearance, he sends Del Boy and Rodney to get blood tests for fear of catching a hereditary blood disease. While they get an all-clear, they appear to have different blood groups, Del's being AB and Rodney's being A, implying that they have different fathers. Reg, having opened the letters before they read it, proclaims that Del is the "Lone Ranger" and begins to alienate Del at every opportunity, especially making references to The Lone Ranger. It transpires that not only did Reg have no such illness, but he sabotaged the letters by adding the B, just to spite Del. Even Granddad, who was happy to see his son again, is disgusted.
Never Live It Down: In the latter episodes, Rodney and Cassandra were fond of bringing up the art contest and subsequent holiday in "The Unlucky Winner Is..." whenever they needed an example of Del's mistreatment of Rodney, to the point where Del even lampshades it in the 2014 Sport Relief episode.
At the very least, nearly everyone agrees that the 2001—2003 trilogy is markedly weaker than the rest of the series.
Some consider the series to have been at its best when it was just two guys and their grandfather/great-uncle trying to pull off "get rich quick" schemes, and that its initial premise was derailed by the introduction of Cassandra and Raquel. At the same time however, others believe that the series was already suffering Seasonal Rot by that point, and that their introduction reinvigorated the format.
The Scrappy: Damien in the 2001-2003 trilogy. An extremely obnoxious Spoiled Brat who speaks almost exclusively in Ali G-style gangster phrases. At one point he freely admits that he wants his own father to go to prison just so he could fit in with the fatherless yobs on the council estate. As James Buckley (Young Del) in Rock and chips proved; you can pull off a rebellious teenager and make him endearing if you try.
Values Dissonance: Del's homophobia, which was Played for Laughs in a way that reflected society's attitudes at the time the early seasons were filmed. Interestingly, the show noted the change in opinions - Rodney is much more accepting, and calls Del out when he suspects that he could have gotten AIDS from an effeminate hairdresser.