HBO's upcoming Harry Potter television series is making significant casting changes for its second season, which is expected to adapt Harry Potter and the Chamber of Secrets. Three key characters—Dobby the house-elf, a young Tom Riddle (Lord Voldemort), and Ginny Weasley—will be portrayed by new actors.

Billy Barratt, known for his roles in Apple TV's Invasion and the horror film Bring Her Back, has been cast as the young Tom Riddle. Barratt previously starred as Nathan Prescott in the television adaptation of the game franchise Life Is Strange and is the youngest recipient of the International Emmy Award for Best Actor for his performance in the BBC TV film Responsible Child. He takes over the role of the young Lord Voldemort from Christian Coulson, who played the character in the 2002 film Harry Potter and the Chamber of Secrets.

Lenny Rush, a recipient of a British Academy Television Award for Best Male Comedy Performance for his work on Am I Being Unreasonable?, has been cast as Dobby the house-elf. In the original film series, Dobby was a CGI character voiced by Toby Jones.

Bonnie Hill will assume the role of Ginny Weasley in the second season, replacing Gracie Cochrane who played the character in the first season. Hill has appeared in Netflix's The Six Triple Eight and Girl Troop vs Aliens, where she also portrayed a character named Ginny. Bonnie Wright famously played Ginny Weasley in the Harry Potter film franchise.

These new additions join previously announced cast members, including Kit Harington as Gilderoy Lockhart, a role originally filled by Kenneth Branagh. The series has also assembled a young core cast, with Dominic McLaughlin as Harry Potter, Arabella Stanton as Hermione Granger, and Alastair Stout as Ron Weasley.

Supporting roles will be filled by a number of actors including John Lithgow as Albus Dumbledore, Janet McTeer as Minerva McGonagall, Paapa Essiedu as Severus Snape, and Nick Frost as Rubeus Hagrid. The ensemble also features Rory Wilmot as Neville Longbottom, Lox Pratt as Draco Malfoy, Leo Earley as Seamus Finnigan, Elijah Oshin as Dean Thomas, Tristan Harland as Fred Weasley, Gabriel Harland as George Weasley, Ruari Spooner as Percy Weasley, Alessia Leoni as Parvati Patil, Sienna Moosah as Lavender Brown, Finn Stephens as Vincent Crabbe, William Nash as Gregory Goyle, Warwick Davis as Filius Flitwick, and Sirine Saba as Pomona Sprout. Additionally, Daniel Rigby will play Vernon Dursley, Bel Powley will portray Petunia Dursley, Paul Whitehouse is set as Argus Filch, Johnny Flynn will be Lucius Malfoy, Bertie Carvel will play Cornelius Fudge, Luke Thallon as Quirinus Quirrell, Katherine Parkinson as Molly Weasley, Amos Kitson as Dudley Dursley, Richard Durden as Cuthbert Binns, Louise Brealey as Rolanda Hooch, Bríd Brennan as Poppy Pomfrey, Leigh Gill as Griphook, and Anton Lesser as Garrick Ollivander.

Harry Potter and the Philosopher's Stone, the first season of the series, is scheduled to premiere on HBO on December 25. Filming for the second season is underway, with these new cast members set to feature prominently.