!!Trivia:
* Both the stars have subsequently played the title character of ''Series/DoctorWho'': Creator/PaulMcGann played the Eighth Doctor, and Creator/RichardEGrant the alternate-timeline Ninth Doctor from the animated serial ''WebAnimation/ScreamOfTheShalka''. It's also worth mentioning that Richard E. Grant also played the Doctor in the comedy special ''Recap/DoctorWhoTheCurseOfFatalDeath''. Much later, Richard E. Grant eventually appears within the Eleventh Doctor's tenure as Dr. Simeon / The Great Intelligence. Finally, according to later interviews by Andrew Cartmel, had ''Doctor Who'' not been cancelled after the 1989 season, the film's third major actor, Richard Griffiths, would have been offered the part of the Eighth Doctor (after having previously been considered for the part of the Fifth and Seventh).
* Creator/PaulMcGann's character is not named in the film, although the script gives his surname as "Marwood". There is LadyMondegreen {{fanon}} that his first name is "Peter", as many fans have independently and distinctly misheard, "He's just had an audition for rep," as "Peter's just had an audition for rep." The name has somewhat become AscendedFanon according to the actors and directors involved. Withnail is not named either, but was widely assumed to have the first name of the person he was based on, Vivian [=McKerrell=], and his first name has been stated to be "Vyvyan" by Grant on Twitter.

!!Trivia-tropes:
* ActorAllusion: The photograph of Creator/RichardGriffiths in Uncle Monty's cottage is from ''The World Cup: A Captain's Tale'' (1982) in which he played a football manager and referee.
* CreatorBacklash: Creator/RichardGriffiths hated talking about the film, not because of the quality of the movie but because he and most of the cast and the crew were shafted by producer Denis O'Brien and never received their proper payments.
* DrinkingGame:
** This very wiki has one: DrinkingGame.WithnailAndI.
** A ''very'' famous version is for the audience to match Withnail drink-for-drink over the course of the film. This means nine and a half glasses of red wine, half a pint of cider, one shot of lighter fluid (contestants are generally allowed to substitute another clear spirit, or vinegar), two and a half shots of gin, six glasses of sherry, thirteen glasses of whisky and half a pint of ale, and one Camberwell Carrot (A doobie. Though, as we would never encourage illegal drug use, a cigarette is a common substitute). And a hangover the size of Norway, or probably death from alcohol poisoning. It is incredibly difficult to progress far beyond the whiskey Withnail drinks late in the First Act before either violent vomiting, unconsciousness, or sleep kicks in. This is probably a good thing, as the reference to alcohol poisoning was not a joke. The entire shebang amounts to roughly ''58'' units of alcohol, which is ''fourteen times'' the maximum recommended daily intake, just under twice the typical lethal dose for an adult male, and three times the weekly intake levels set by the UK Health Board. The film's running time is 107 minutes...[[note]]A wiser version is to pour a single glass of each of Withnail's drinks, plus vinegar, plus cigarette, and take a ''sip'' when he drinks.[[/note]]
* DyeingForYourArt: Creator/RichardEGrant was hired on the proviso that he lost weight. Ironically he had just been trying to gain some weight through working out because he thought was too skinny. He went on a diet of protein shakes to achieve his gaunt look in the film.
* EnforcedMethodActing:
** The first drink consumed on screen is supposed to be lighter fluid. Vinegar was used in the filming (although it was water in the rehearsals), and the reaction of Creator/RichardE.Grant (who's actually teetotal in RealLife) was genuine.
** Further to the Enforced Method Acting, the director insisted on getting Richard E. Grant utterly plastered with him before shooting started. Grant, who's teetotal due to not breaking alcohol down properly, got utterly plastered and, as Robinson put it, finally knew what it was like to be ''that'' drunk.
* IronyAsSheIsCast: Creator/RichardEGrant is physically incapable of drinking alcohol, due to his body not producing a certain enzyme, which forces him to throw any alcohol up minutes later.
* MidDevelopmentGenreShift: Bruce Robinson originally wrote the film as a novel.
* RealitySubtext:
** Something that makes the last twenty minutes even sadder. This was the first film of both Creator/RichardEGrant and Creator/PaulMcGann. At the time, [=McGann=] was an established stage and TV actor, and while this was his first film role, he knew he still had a career waiting for him if his attempt to move into films didn't pan out. Grant, however, had no idea if this was going to be his one and only film or not and so he knew how upset and jealous Withnail was feeling. But as we all know, Grant's fears were unfounded and this film even managed to make him a sex symbol for a while.
** Robinson based Withnail on his RealLife friend and actor, Vivian [=MacKerrell=] who actually did drink lighter fluid once. Robinson has attributed his friend's early death from throat cancer to this incident.
* ScrewedByTheNetwork: Bruce Robinson's mistreatment by Creator/HandmadeFilms.
* StarMakingRole: For Creator/RichardEGrant.
* ThrowItIn:
** [[http://luminarynyc.files.wordpress.com/2010/05/withnail.jpg Withnail's grimace]] complete with a pork pie trying to escape from his mouth was completely accidental.
** In the tearoom scene, Creator/RichardEGrant breaks out laughing. This wasn't scripted, but every time he spoke, he could hear the snorting of the dogs belonging to the old ladies at the table behind. He thought that this was someone laughing and kept {{Corpsing}}. After too many re-takes, the director gave up and kept the laughter in.
* WhatCouldHaveBeen:
** Creator/DanielDayLewis was offered but declined the role of Withnail. Among the other actors who tested for it were Creator/KennethBranagh, Creator/KennethBranagh and Edward Tudor-Pole.
** The film's original ending had Withnail drinking wine from the shotgun before killing himself with it.
* WordOfSaintPaul: Via Twitter, Creator/RichardEGrant said that Withnail's first name is Vivian, the same as the character's inspiration Vivian [=MacKerrell=].
* WriteWhoYouKnow:
** The film is based on Robinson's own life in London, albeit dramatized and condensed a bit. Withnail is based on his friend Vivian [=MacKerrell=], who later died of throat cancer.
** Robinson maintains he received unwanted advances from Italian filmmaker Creator/FrancoZeffirelli whilst playing Benvolio as a young actor in the 1968 film adaptation of ''Theatre/RomeoAndJuliet''. Uncle Monty is loosely based on this experience, and some of his dialogue with Marwood is supposedly quoted verbatim from Zeffirelli's attempts to seduce Robinson.
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