WARNING: The following article contains spoilers for Joe Cornish's The Kid Who Would Be King, in theaters now.

Fan-favorite actor Patrick Stewart is able to bring gravitas to sci-fi and fantasy, humanity to the works of William Shakespeare, and bizarre energy to comedies. It's certainly not uncommon to see him indulging in all three at the same time, in the same role.

Such is the case for his performance as Merlin in The Kid Who Would Be King, a 21st-century take on Arthurian legend by writer/director Joe Cornish (Attack the Block). While the wizard spends most of the film in a more youthful form (played by Angus Imrie), every time Merlin reverts to his older appearance, it's an absolute delight, all due to Stewart.

The Wizard Did It

Merlin plays a major supporting role throughout The Kid Who Would Be King. While he doesn't directly lead young Alex (Louis Ashbourne Serkis) to Excalibur, he does arrive not long after the boy has claimed the mystical sword. Merlin delivers exposition to Alex and his best friend Bedders (Dean Chaumoo), but neither of them takes him too seriously. They don't believe the gangly teen in front of them could be the Merlin -- that is, until he reverts to his older form. Stewart quickly unleashes a wave of magic, not only wrecking the apartment but also showing the boys a vision of their doomed lives if Morgana, ancient enemy of King Arthur, breaks free of her prison and attacks the modern world.

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Stewart delivers the warning with a booming voice, projecting the wizard of legend. But then he falls back onto the couch, grabs a falling bucket of fried chicken, and complains about how exhausting it is to go all out. It's a terrific moment of comedy, showcasing the sheer power of the wizard, as well as the frailty of the man. Stewart only appears when things are at their darkest, most notably when the children are confronted by Morgana in the film's climax. Although he believes in Alex and his friends, there's a hint of desperation when he assures that they can defeat her. Merlin cares about these children, but perhaps never completely believes in them. This is a Merlin who is tired, something Stewart conveys without making the character pitiful or self-defeating.

Ultimate Power

Merlin is in this form when he says goodbye to the heroes. While he'd assumed the teen body for most of their journey, it's in his elder form that he wishes the children well and assures them of their growth. It suggests this old body is his true one, and that his teen self was used out of necessity. They're the same person, but Merlin feels relaxed for the first time in the film. Stewart plays the same character, but with a warmer air to him. In this moment, his age really is a factor in the scene's emotions, and it's something Stewart pulls off splendidly.

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There's a lot to like about The Kid Who Would Be King. But one of the best aspects of the film is seeing Stewart tackle such a legendary figure, and with a the quiet confidence to do it well. He's funny, moving and even heartbreaking. While Angus Imrie does a great job as the teen Merlin, we wouldn't have minded one bit if Stewart portrayed the wizard throughout the film.

Writer/director Joe Cornish's The Kid Who Would Be King stars Louis Ashbourne Serkis, Tom Taylor, Rebecca Ferguson, Patrick Stewart, Rhianna Dorris, Denise Gough, Dean Chaumoo and Nathan Stewart-Jarrett.