With the filming of the Harry Potter franchise spanning a whopping 10 years, it's not a massive surprise that some actors had to be replaced.
However, 27 is a fairly hefty number, and actors were re-cast for various different reasons.
According to Morgan Ross, who runs Movie Flame, 23 characters were re-cast and a total of 27 were replaced - with more than one replacement for certain characters.
Some of these recasts range from background characters to starring actors.
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And the hefty number also includes the Fantastic Beasts series as part of the whole of the Harry Potter franchise.
The Fat Lady
Viewers first catch sight of the portrait of the Fat Lady in Harry Potter and the Philosopher's - or Sorcerer's Stone if you're American - where the character is played by Elizabeth Spriggs.
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However, the singing and drunken Gryffindor common room guard is later replaced in Prisoner of Azkaban by comedian and actor Dawn French.
The Grey Lady (Helena Ravenclaw)
Nina Young played the ghost in the first two movies before the role was taken over by Kelly Macdonald in The Deathly Hallows Part II.
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In the later film, the Grey Lady is later revealed to be Helena Ravenclaw as she tells Harry where to locate her mother's lost diadem - which had become one of Lord Voldemort's Horcruxs.
Katie Bell
Bell is one of the Gryffindor Quidditch team chasers and was originally played by Emily Dale.
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Dale had no lines as Katie in the first two movies, didn't feature in the next three and was later replaced by Georgina Leonidas in the sixth movie, which sees Bell tortured by a cursed opal necklace.
Angelina Johnson
Another chaser in the Gryffindor Quidditch team, Angelina Johnson was originally played by Daniella Tabo in the first three films.
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However, Tiana Benjamin took over the role when Angelina became Fred Weasley's date to the Yule Ball in The Goblet of Fire.
Alicia Spinnet
Leilah Sutherland was the first actor to portray the third Gryffindor Quidditch team chaser.
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She was later replaced by Rochelle Douglas in Chamber of Secrets.
Susan Bones
A Hufflepuff half-blood witch, Susan was first played by one of the franchise's director and producers Chris Columbus' daughter, Eleanor.
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After the first two movies, the character next appeared in the franchise in The Deathly Hallows - with Emma Jayne-Corboz taking over the role.
Ernie Macmillan
Hufflepuff student Ernie was originally played by Louis Doyle.
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But in Deathly Hallows, Jamie Marks took over the role.
Lavender Brown
Ron's obsessive girlfriend who made most viewers retch every time she called him, 'Won won,' was actually played by three different actors.
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Lavender was originally played by Kathleen Cauley in Chamber of Secrets and later replaced by Jennifer Smith in Prisoner of Azkaban, before the character was recast for a third time - with Jessie Cave taking on the role.
The recast also faced backlash from some fans due to a white actor taking over from two Black actors as soon as the role became more prominent.
Parvati Patil
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Lavender's best friend is first portrayed by Sitara Shah.
However, as per Screen Rant, Shah was replaced by Shefali Chowdhury because she looked too young to continue playing the role - particularly in Goblet of Fire when Parvati and her twin Padma go to the Yule Ball with Harry and Ron.
Padma Patil
In Prisoner of Azkaban, Padma is played by Sharon Sandhu before Afshan Azad took over the role in time to be Ron's date to the Yule Ball.
Cedric Diggory
Movie Flame's Ross notes you have to be 'a true fan' to have noticed the recasting of Hufflepuff's Cedric.
At first mention, you'll likely think of Robert Pattinson's heart-wrenching and heroic portrayal in The Goblet of Fire.
However, in Prisoner of Azkaban, Cedric can be spotted playing as the seeker for Hufflepuff in the Quidditch match which sees Harry fall from his broom - played by stuntman Joe Livermore.
Pansy Parkinson
Best mate to Draco Malfoy and, of course, a Slytherin, Pansy has been played by a whopping four different actors.
She is first portrayed by Katherine Nicholson, and Lauren Shotton then took over the role.
Pansy was later recast as Genevieve Gaunt before Scarlett Hefner saw the character through the rest of the franchise.
Bill Weasley
Richard Fish was the first actor to take on the role, however, he didn't have any lines during his five-second appearance in The Prisoner of Azkaban.
The eldest child of Arthur and Molly Weasley only returns for The Deathly Hallows and was re-cast for the final movies, played by Domnhall Gleeson.
Gleeson's father is Brendan Gleeson - the actor who played Alastor 'Mad-Eye' Moody in The Goblet of Fire.
Tom the Innkeeper
The character was recast for The Prisoner of Azkaban and taken in a very different direction.
Derek Deadman's jolly portrayal in Philosopher's Stone contrasts greatly with Jim Tavaré's hunchbacked recreation of the character, who under director Alfonso Cuarón, created a much more sinister version of the innkeeper.
Elphias Doge
The Ministry of Magic jurist, member of the Order of the Phoenix and one of Dumbledore's oldest friends was first played by Peter Cartwright.
David Ryall later took over the role in The Deathly Hallows.
Griphook
American actor Verne Troyer - best known for the Austin Powers movies - played the role of the goblin who escorts Harry and Hagrid through Gringotts Bank in Philosopher's Stone.
However, the character was actually voiced by Warwick Davis.
Davis had already played Professor Filius Flitwick in the franchise and took on the additional role of Griphook in Deathly Hallows Part One and Two.
Kreacher
The House of Black house-elf - who it's fair to say, wasn't a massive fan of Harry - was voiced by two different actors.
Timothy Bateson was the first actor to take on the role, however, after Bateson sadly passed away in 2009, the role had to be re-cast and Simon McBurney took over.
Walden Macnair
The Dark Wizard and Death Eater briefly worked at the Ministry of Magic before returning to work for he who must not be named.
Walden was originally played by Peter Best in Azkaban before Ashley Artus took over the role in Goblet of Fire, however, Best returned to the character in Order of the Phoenix.
Walden was then re-cast for a third time for both parts of The Deathly Hallows - played by Granville Saxton.
Tom Riddle
The spine-tingling character of teenage Voldemort - Tom Marvolo Riddle - first appears in Chamber of Secrets played by Christian Coulson.
In the sixth film, Riddle was re-cast, with Frank Dillane taking on the role.
Lord Voldemort
Even he who must not be named received a recast - twice as an adult as well as a teenager.
Richard Bremmer first took on the terrifying role in the fiery scenes of Philosopher's Stone.
The Dark Lord was later portrayed by Ralph Fiennes.
Aberforth Dumbledore
The younger brother of Albus Dumbledore was played by Jim McManus during his fleeting appearance in Order of the Phoenix as a barman.
The role was later taken over by Ciarán Hinds for Deathly Hallows Part Two.
Albus Dumbledore
Dumbledore was played by Richard Harris in the first two movies.
However, the actor sadly passed away and so the Hogwart's headmaster was eventually recast as Michael Gambon.
Gellert Grindelwald
Fantastic Beasts is considered by many Harry Potter fans as still being part of the infamous franchise.
The character of Grindelwald started off being portrayed by Johnny Depp, however, Warner Bros cut ties with Depp as a result of the accusations and legal battles between Depp and his former partner, Amber Heard.
In The Secrets of Dumbledore, the role of Gellert was subsequently taken over by Mads Mikkelsen.
Topics: Harry Potter, JK Rowling, Film and TV, Entertainment
Poppy Bilderbeck