Harry Lloyd has been cast as Professor X in Legion season 3. Noah Hawley's Legion has been one of the most unusual superhero shows to date, a cerebral series in which reality itself often seems to be in flux. In part because it explores the world through the eyes of David Haller, an Omega Level mutant diagnosed with Dissociative Identity Disorder and locked in battle against the ruthless psychic entity known as the Shadow King.
Legion is loosely inspired by the X-Men comics, where David Haller is the son of the X-Men's founder Charles Xavier and his lover Gabrielle. Gabrielle kept David's very existence a secret from his father for years, and Xavier was shaken to the core when he realized that his son possessed both almost unlimited power and serious mental instability. In the comics, each of Legion's different personas can tap into a different superhuman ability, and some of them are very dangerous indeed.
Although David's personal history has been subtly rewritten for the small screen, the series has been teasing Professor X for quite some time. Now Legion's Twitter account has officially confirmed that both Charles Xavier and Gabrielle Haller have been cast for guest roles in season 3. Harry Lloyd (Marcella, Hang Ups, Counterpart) will be playing Charles Xavier, while Stephanie Corneliussen (Mr. Robot, Deception) will be stepping in as Gabrielle Haller. The tweet describes these as "guest casting," suggesting they won't have a major role, and indeed may only play a brief cameo.
Legion is one of two Marvel TV series produced by a partnership between Marvel Television and Fox. This is actually the first time any of the major X-Men will appear in one of these TV shows; in fact, The Gifted has had to go to great lengths to avoid even dropping the name "Magneto," a rather ridiculous decision given it features Magneto's daughter Polaris. It's been heavily implied this was for legal reasons, so presumably Noah Hawley had to jump through quite a few legal hoops to be able to use Professor X in Legion. The cast had occasionally talked about trying to get Patrick Stewart to cameo, but it seems Hawley has instead gone for recasting the role.
It's been confirmed that Legion season 3 will bring the series to an end, in accordance with Hawley's plans all along. Hopefully this latest news means that Legion will ultimately bring David face-to-face with his long-absent parents, rather than simply featuring them in a flashback scene of some kind. That would be a fitting end for David's story, as he finally finds the family he's always longed for.