Harry Potter's reunion special on HBO Max has multiple actors from the original movies missing. Here's everyone who isn't in Return to Hogwarts.

Several main Harry Potter actors are missing from the Harry Potter 20th Anniversary: Return to Hogwarts reunion special. To celebrate the 20th anniversary of Harry Potter and the Sorcerer's Stone's release, Warner Bros. and HBO Max made sure to celebrate the franchise in style. This included bringing Harry Potter stars Daniel Radcliffe, Emma Watson, and Rupert Grint back together to discuss the franchise's legacy. The reunion special brought back plenty of other veterans from the franchise, but it couldn't use everyone.

Throughout the duration of the original eight-film Harry Potter franchise, the movies became loaded with characters and prominent actors. Return to Hogwarts managed to bring back some of the biggest characters who were featured alongside Harry Potter, Hermoine Granger, and Ron Weasley. The reunion special's confirmed cast list includes Jason Isaacs (Lucius Malfoy), Tom Felton (Draco Malfoy), Ralph Fiennes (Voldemort), Gary Oldman (Sirius Black), Helena Bonham Carter (Bellatrix Lestrange), Robbie Coltrane (Hagrid), Imelda Staunton (Dolores Umbridge), Bonnie Wright (Ginny Weasley), Matthew Lewis (Neville Longbottom), Evanna Lynch (Luna Lovegood), Alfred Enoch (Dean Thomas), Ian Hart (Professor Quirrell), Mark Williams (Arthur Weasley), and James and Oliver Phelps (Fred and George Weasley).

Due to a variety of reasons, not every prominent person associated with the Harry Potter franchise returned for Return to Hogwarts. Series creator J.K. Rowling declined an invitation to appear, while other main actors like Alan Rickman and Richard Griffiths passed away years ago. Still, there are various actors who played major roles in the Harry Potter movies that aren't in Return to Hogwarts. Here are the biggest actors missing from the reunion special.

Maggie Smith

Dame Maggie Smith didn't return for Harry Potter 20th Anniversary: Return to Hogwarts. She played Professor Minerva McGonagall in all eight Harry Potter movies, making her absence from the reunion special one of the most notable. McGonagall rose through the wizarding school's ranks during Harry Potter's run. She was a transfiguration professor and Head of Gryffindor House leading up to the first Harry Potter movie. McGonagall went on to become the Headmistress of Hogwarts after Voldemort's defeat during the Second Wizarding War, showing she was one of the most formidable witches in the world of Harry Potter.

Michael Gambon

Michael Gambon starred in six of the original Harry Potter movies as Albus Dumbledore. He took over the role in Harry Potter and the Prisoner of Azkaban following the death of Dumbledore's original actor Richard Harris. Gambon's time as the Headmaster of Hogwarts and owner of the Elder Wand saw the character become a more prominent part of the franchise. Albus guided Harry throughout his journey as a young wizard up until Snape killed him in order to keep up the ruse to protect Harry.

Julie Walters

Julie Walters didn't return for Harry Potter's reunion special to reflect on her time as Molly Weasley. Her absence is quite noticeable considering every other member of the Weasley family is featured. Walters originally played Molly Weasley in seven of the first eight Harry Potter movies, as Harry Potter and the Goblet of Fire left her out. Molly Weasley's affable and kindhearted demeanor belied her inner ferocity. She eventually went on to become a member of the Order of Phoenix and killed Bellatrix Lestrange during the Second Wizarding War.

David Thewlis

David Thewlis is also missing from Harry Potter 20th Anniversary: Return to Hogwarts. He played Remus Lupin, a powerful wizard and werewolf, in five entries in the franchise. Thewlis joined the series in Harry Potter and the Prisoner of Azkaban and made his final appearance in Harry Potter and the Deathly Hallows: Part 2. Remus was killed by Antonin Dolohov during the Battle of Hogwarts. Prior to his death, he was close friends with Harry's parents and taught at Hogwarts.

Jim Broadbent

Harry Potter's reunion special cast didn't include Jim Broadbent either. The accomplished actor played Professor Horace Slughorn in two installments. Broadbent joined the series with Harry Potter and the Half-Blood Prince and only returned for Harry Potter and the Deathly Hallows: Part 2. Slughorn's role in the series revolved around Voldemort, as he was the one who told Tom Riddle about Horcruxes. He participated in the final battle against Voldemort, turning against him, and retired for a second time from teaching afterward.

Brendan Gleeson

Brendan Gleeson also didn't make the cut to appear in Return to Hogwarts. He joined the franchise as Alastor "Mad-Eye" Moody in Harry Potter and the Goblet of Fire. He returned for Harry Potter and the Order of the Phoenix and Harry Potter and the Deathly Hallows: Part 1. Moody's role saw him become one of Hogwarts' revolving door of Defense against the Dark Arts professors before joining the second Order of the Phoenix. He later died when Voldemort's Death Eaters attacked Harry and the Dursleys.

Harry Melling

Harry Melling played Harry Potter's cousin Dudley Dursley throughout the franchise, appearing in five of eight movies. Melling wasn't part of Harry Potter and the Goblet of Fire, Harry Potter and the Half-Blood Prince, and Harry Potter and the Deathly Hallows: Part 2. Although Dudley often bullied Harry when they were younger, he eventually began treating him better after Harry saved him from Dementors.

Devon Murray

Devon Murray is another actor missing from Harry Potter's reunion special Return to Hogwarts. He appeared in all eight of the original movies as Seamus Finnigan, who went on to become a secondary friend of Harry's and was a member of Gryffindor House. Seamus fought in the Battle of Hogwarts in Harry Potter and the Deathly Hallows: Part 2 and survived the widespread battle. Murray is one of only a few actors to appear in all eight films and not be featured when the HBO Max reunion special releases.

Josh Herdman

Josh Herdman also appeared in all eight Harry Potter movies but was left out of Harry Potter 20th Anniversary: Return to Hogwarts. He played Gregory Goyle, a Slytherin and son of a Death Eater, throughout the series. Goyle participated in the Battle of Hogwarts alongside his best friend Draco Malfoy, and he was later saved by Ron and Hermione following their battle.

Warwick Davis

Warwick Davis isn't part of the Harry Potter reunion special's cast, either, which is a surprise considering he played multiple roles throughout the original eight movies. Davis played Griphook the Goblin in Harry Potter and the Sorcerer's Stone and the two-part franchise finale. He was also Hogwarts Charms professor Filius Flitwick in every movie except Harry Potter and the Deathly Hallows: Part 1 as well as being the Head of House Ravenclaw.

Fiona Shaw

Fiona Shaw is also missing from Harry Potter 20th Anniversary: Return to Hogwarts. The multiple Emmy-nominated actress played Petunia Dursley in the franchise and appeared in five of eight movies. Her role as Harry's Aunt Petunia began in Harry Potter and the Sorcerer's Stone, where she treated Harry poorly. Harry Potter and the Deathly Hallows: Part 1 marked her final appearance as she and her family went into protection to hide from Voldemort.

More: Harry Potter Movie Sequel: What Every Original Star Has Said About Returning