He pulls it out, unaware that it's the legendary Excalibur, once owned by King Arthur who long ago banished his half-sister Morgana (REBECCA FERGUSON) to the underworld for having turned to evil and thus ending up at odds with him and the knights of his round table. Alex also doesn't know that Morgana has been awakened by unrest and divisions around the world and is growing stronger by the day, desiring to return to the surface, claim Excalibur for her own and enslave everyone.

But Arthur's former wizard, Merlin (PATRICK STEWART), is aware of this and that she'll make her appearance in just four days during a solar eclipse. Accordingly, he adopts the guise of a teenager, Mertin (ANGUS IMRIE), in order not to scare away Alex while informing him of this development and educating him about what to do.

Alex initially doesn't believe any of it but after a run-in with Morgana's demon-like undead knights that emerge from the ground at night and come after him and Bedders, he changes his mind. Trying to enlist the aid of Lance and Kaye and turn them from enemies into allies, Alex tries to summon up the courage for the battle that will soon envelop him and his friends.

And that's because doing so runs the risk of putting viewers into comparison mode where they pit what they're watching against the referenced movie -- which almost never is a good idea -- when not otherwise simply distracting audiences and taking them out of the world that's been created.

Despite such storytelling and cinematic experience consequences, that's exactly what occurs at a certain moment in "The Kid Who Would Be King." Of course, since it's a kid-oriented and kid-friendly spin on the old King Arthur and the Knights of the Round Table tale, any past movies based on that legend will automatically come to mind. But that's to be expected and is certainly unavoidable considering the premise here.

Instead, sort of out of the blue, it's pointed out that the saga of our protagonist, 12-year-old Alex Elliott (Louis Ashbourne Serkis), is fairly similar to that of Luke Skywalker and Harry Potter (in that all feature seemingly ordinary characters without a father who find themselves drawn into an extraordinary tale filled with magic, danger, and adventure where they're forced into the role of unlikely hero to battle evil).

When that happened during this pic's two-hour runtime -- courtesy of writer/director Joe Cornish -- I felt myself cringe a bit as it did unnecessarily take me out of the proceedings (even if it would be something one of these kid characters would likely think). Thankfully, it was just a momentary detour of my attention in what's otherwise a fairly entertaining and engaging (not to mention umpteenth retelling) of the old medieval tale.

After a brief animated prologue about King Arthur vanquishing his half-sister to the underworld long ago, the story revolves around young Alex who doesn't see any escape from being a "nobody" just like his friend Bedders (Dean Chaumoo) and must contend with a duo of bullies (Tom Taylor and Rhianna Doris) who repeatedly harass them at school and about parts of London.

It's during such a chase where Alex takes a spill off a partially demolished building at a construction site and discovers, of all odd things, an old medieval sword sticking up out of some concrete remains. He yanks it out and returns home where he lives with his single mom (Denise Gough) and puts the sword in the closet.

But it summons him with its slow pulsing glow when a demon of sorts emerges from his yard at night and enters his house. If not for the actions of a new classmate, Mertin (Angus Imrie), Alex would certainly be a goner. That encounter and the life-saving magic of his new friend cause the boy to realize the newfound sword could very well be the legendary Excalibur.

Mertin, who's quite proud of his fake name "hiding" the fact that he's really Merlin (Patrick Stewart when in old age mode), informs the unlikely hero that he must do battle with Arthur's half-sister, Morgana (Rebecca Ferguson), who's been resurrected by the unrest and division around the world due to the rise of dictators and such. And he must defeat her before the end of a total solar eclipse that's just four sunrises away. So, he must turn his enemies (the bullies) into allies and raise a kid-army to deal with the villain, all while learning how to be both a warrior and leader.

Serkis is appealing in the lead role and he and Chaumoo make for a fun comedy-adventure duo. Taylor and Doris are decent as the bullies, but it's Imrie who steals the show as Merlin in the guise of a teen. He's a blast to watch and I wouldn't be surprised to see him in some sort of spin-off tale. Unfortunately, the villain is the film's weak point. While she's portrayed as evil and eventually turns into some sort of half-human, half-dragon monster hybrid, her modus operandi -- to return to the surface, obtain and then possess Excalibur, and enslave everyone -- is fairly simplistic and not terribly interesting (especially as compared to, say, Josh Brolin's Thanos in the recent "Avengers" flick).

It's certainly not a fatal flaw, but that lack of a decent villain and a running time that's twenty to thirty minutes too long knock a few points off the final score. But at least everything else -- the appealing leads, the adventure and so on -- works well enough that you don't mind and don't end up distracted when that Luke and Harry comparison suddenly pops up. "The Kid Who Would Be King" rates as a 6 out of 10.