Robbie Coltrane was the very first person to be cast.

Richard Harris only agreed to taking the part of Albus Dumbledore after his eleven year old granddaughter threatened never to speak to him again. Patrick McGoohan was originally offered the role but had turned it down due to health reasons.

Author J.K. Rowling insisted that the principal cast be British and she got her wish, with two exceptions - Richard Harris was, of course, Irish, and Zoë Wanamaker, though she has made her name as a "British" actress, was actually born in the United States. Other non-Brits in the cast include Verne Troyer, born in Michigan, USA, who plays Griphook (the second Goblin in Gringots' Bank) and Chris Columbus daughter, Eleanor Columbus, who played Susan Bones.

The hut used during the filming as Hagrid's hut has since been demolished in case fans of the film swamped it.

The tabby cat used ran away during filming and came back two days later.

While the movie used Platforms 4 and 5 at Kings Cross to represent platforms 9 and 10, there is, in fact a "Platform 9 3/4" at Kings Cross. It's located in the walkway area between the intercity section and the section where the real platforms 9 and 10 are, and was obviously put there for fans of Harry Potter.

At one point, when Harry, Ron, and Hermione are approaching Hagrid, he can be seen playing a wind instrument. He is playing the Hedwig's Theme.

Among the portraits on the shifting staircase, you can clearly see a painting of Anne Boleyn, King Henry VIII's second wife and the mother of Queen Elizabeth I. Anne Boleyn was popularly believed to be a witch.

This movie has the distinction of opening on more screens in the USA than any other (3762).

By February 2002 this was the second highest grossing film worldwide after Titanic (1997).

Daniel Radcliffe learned he'd won the role of Harry Potter while in the bathtub.

Warner Bros. originally considered making the entire "Harry Potter" series as a set of CGI animated films, or attempting to combine several of the novels into a single movie. The studio's reasoning mainly had to do with concern over the rapid aging of child actors-if production ran too long on any of the films, or if production was delayed between sequels, the leading actors might have to be recast. Author J.K. Rowling vetoed both the ideas of combining books and an animated film, so the studio decided instead to produce all seven (later eight) films back to back so the same child actors could play their roles in every film.

On the Quidditch trophy that has Harry's father's name on it, there are additional inscriptions for M. McGonagall and R.J.H. King. The latter being a reference to John King, the supervising art director on the film.

The inscription around the Mirror of Erised says: "Erised stra ehru oyt ube cafru oyt on wohsi". Reading the inscription backwards it says, "I show not your face but your heart's desire."

The word 'bloody' appears in the film six times, along with one 'arse', one 'bugger', and two 'blasted's. This, and some very scary scenes in the haunted forest, led to its PG certificate.

The film reveals that the 12th use for dragon's blood is an oven cleaner.

Nicholas Flamel, mentioned as the creator of the Philosopher's/Sorcerer's Stone, was actually a real alchemist who was believed by some people to have produced the Philosopher's Stone and who has mysterious circumstances surrounding his "death". It is rumored that he might still be alive and, if so, he would be about the age given in the book and movie.

The Hogwarts motto, "Draco dormiens nunquam titillandus" means "never tickle a sleeping dragon".

Three owls play Hedwig: Gizmo, Ook and Sprout, but mainly Gizmo.

Warwick Davis, who played Professor Flitwick and the first Gringotts Goblin, also provided the voice for Griphook who was physically played by Verne Troyer.

In the original draft, Drew Barrymore, a self-proclaimed Harry Potter fan, had a cameo.

Rosie O'Donnell and Robin Williams were two of the celebrities who had asked for a role in the movie without pay. However they did not film any scenes for the movie.

Tim Roth was a leading contender for the role of Professor Severus Snape. Roth dropped out of contention, however, to pursue his role as General Thade in Tim Burton's adaptation of Planet of the Apes.

In the script, the flashbacks to Voldemort killing Harry's parents were written by J.K. Rowling herself. The producers knew she was the only one who knew exactly what happened.

The "Hogwart's Express" locomotive portrayed in this film, a 1937 4-6-0 "Hall" class steam engine number 5972, originally belonged to the Great Western Railway and went under the name of "Olton Hall".

Alan Rickman was hand-picked to play Snape by J.K. Rowling.

Robbie Coltrane was also handpicked by J.K. Rowling to play Hagrid.

In the troll scene in the girl's bathroom, Daniel Radcliffe isn't actually on the troll's neck, because the motions would have snapped his neck; therefore, his image was digitally added.

In the trophy cupboard, to the right of the Quidditch trophy, you can see the "Service to the School" trophy with part of "Tom M Riddle" engraved on it.

The Wizard's chess-set Harry and Ron were playing, the red queen is from the Lewis Chessmen, the most important of all chess pieces dating from the 12th Century. They were found in 1831 on a beach in Uig, Lewis. 78 pieces were recovered in all, and are now in the care of the National Museum of Scotland and in the British Museum in London.

For the Gringotts interior scenes, the Australian High Commission in London was used. The exteriors are the Silver Vaults located not far from the Australian High Commission.

Gabriel Thomson was considered for the role of Harry.

All the cars in Privet Drive are Vauxhalls, no matter the time period. The Dursleys own a silver 2000 Vauxhall Vectra estate. All other cars parked in the drives are Vectra estates in the present day, with Astra Belmont and Cavalier saloons from the late 1980s in the pre-titles prologue.

The street that Harry and Hagrid walk down to get to the Leaky Cauldron is the same street Sean Connery is parked in waiting for Catherine Zeta-Jones to leave the antiques shop in Entrapment.

David Thewlis, who later played Professor Lupin in Harry Potter and the Prisoner of Azkaban, was considered for the role of Professor Quirrell.

In the film, the scar on Harry's forehead is off-center. This was done at J.K. Rowling's request. Due to the artwork on the covers of her books, many people have assumed that his scar is supposed to be in the center of his forehead. The books, however, never specify exactly where on his forehead the scar is located.

At one time, Alan Parker was considered for the director's job.

The exterior used for King's Cross Station is actually St Pancras Station which is just down the road. This was used because the facade of St Pancras is more visually appealing than that of King's Cross.

Platform 9 3/4 was filmed at Kings Cross, but on platforms 4 and 5. J.K. Rowling has admitted that she mixed up the layout of London's King's Cross railway station when she assigned the Hogwarts Express to platform 9 3/4, reached by using magic between platforms 9 and 10. She meant the location to be in the Inter-City part of the station, but 9 and 10 are actually among the rather less grand suburban platforms. The movie conformed to Rowling's original intent: the platforms seen as 9 and 10 are in real life inter-city platforms 4 and 5.

John Williams composed a piece of music specifically for the movie's trailer, and it is found on the soundtrack as "The Prologue". As of March 2002, he has done this only once before, for Steven Spielberg's Hook. (However, on the collector's edition of the soundtrack for Jaws, a previously unreleased track appears called "Shark Attack" - this was only used in the trailer for that movie - in 1975.)

Robbie Coltrane's 6'10" body double for Hagrid is former England rugby international, Martin Bayfield.

Screenwriter Michael Goldenberg wrote a draft of the script but was ultimately rejected by David Heyman in favor of Steve Kloves' draft. Heyman however was impressed with his draft and was subsequently brought in to write the script for Harry Potter and the Order of the Phoenix when Kloves backed out to commit on a personal project.

Steven Spielberg reportedly wanted Haley Joel Osment for the part of Harry.

The last name Dumbledore means "Bumblebee" in Old English.

West Anglia Great Northern Trains, the company that owns "Platform 9-3/4", affixed one-quarter of a luggage trolley forwardly "disappearing" into the wall so as to allow fans (and their parents) to take pictures of themselves seeming to disappear into the wall.

During filming, Daniel Radcliffe changed the screen on Robbie Coltrane's cellphone to Turkish. Coltrane had to phone hair designer Eithne Fennel's Turkish father in order to find out Turkish for "Change Language".

Director Chris Columbus wanted to work with DP John Seale and asked the studio to hire him to shoot the picture, but at that time Seale was committed to shooting Timeline. However, production delays for the latter film enabled Seale to be available for the movie's photography period.

The platform attendant at Kings Cross who asks Harry, "You think you're funny, do you?" actually works for GNER. He is, however, a train manager and not a platform attendant.

Liam Aiken was originally given the role of Harry, but a day later the offer was revoked when it was discovered that he wasn't British (Aiken had previously worked with director Chris Columbus).

In addition to Steven Spielberg, other candidates for the director's job were Jonathan Demme, Brad Silberling and Terry Gilliam. Gilliam was J.K. Rowling's initial favorite but the studio finally picked Chris Columbus to direct because he had experience directing child actors. Columbus was also asked many times by his daughter to direct and he agreed after he read her copy of the book.

Ron's choice of opening in the final chess match is called Center Counter Opening (or Scandinavian Defense), which, due to its asymmetrical nature, is said to be a highly unpredictable and difficult opening for either side, that rarely results in a draw.

The filmmakers attempted to go the extra mile of matching the kid's appearances to how the novel describes them, by fitting Daniel Radcliffe with green-colored contact lenses, and similarly make Emma Watson wear fake buck teeth. But when Dan's eyes reacted strongly to the contacts, and Emma couldn't talk clearly with the fake teeth in her mouth, these ideas were dropped.