In a scene from “Lyle, Lyle, Crocodile,” the title character (voice of Shawn Mendes) takes a bath. Sony Pictures/Columbia Pictures

The title character of “Lyle, Lyle, Crocodile” may be a coldblooded reptile – in this case, one who sings – but never you worry: This family flick delivers enough pulse-quickening earworms and warmth to melt even the iciest of hearts.

Not that Lyle himself, voiced by pop star Shawn Mendes in this blend of live action and computer animation, is anything but lovable. Following the child-befriends-a-misunderstood-monster paradigm of “E.T.: The Extra-Terrestrial” and “The Iron Giant,” “Lyle, Lyle, Crocodile” takes the bite out of its razor-toothed hero by imbuing him with expressive eyes, a sheepish demeanor and Mendes’s silky tenor. Although Lyle doesn’t talk – a trait carried over from Bernard Waber’s beloved picture book series, begun in 1962 with “The House on East 88th Street”– this version of the character does sing, even if his stage fright keeps the world from understanding the gentle soul beneath his scaly exterior.

It’s a crafty conceit that allows screenwriter Will Davies to recast Lyle’s tale as a pop-rock musical by way of Benj Pasek and Justin Paul, the hit-churning songwriters behind “The Greatest Showman,” “Dear Evan Hansen” and “La La Land.” Here, they collaborate with Ari Afsar, Emily Gardner Xu Hall, Mark Sonnenblick and Joriah Kwamé to compose original tunes worthy of that catchy catalogue. Among them: the soaring anthem “Top of the World,” the power ballad “Carried Away” and the charming duet “Take a Look at Us Now.”

That last song complements Mendes’s polished pipes with the rawer vocals of Javier Bardem, who plays down-and-out magician Hector P. Valenti with vaudevillian verve. Sporting a thick mustache and a thinning mop of hair, the endearingly eccentric character looks after Lyle in the attic of a Manhattan brownstone – that is, until the showman skips town and leaves the family that moves in to discover a reptilian housemate with a love of caviar and bubble baths.

From left, Constance Wu, Winslow Fegley, Lyle the crocodile (voice of Shawn Mendes) and Javier Bardem in “Lyle, Lyle, Crocodile.” Sony Pictures/Columbia Pictures

Lyle’s companionship is a balm for tween Josh (Winslow Fegley), an anxious kid struggling to fit in at his new school, as the two outcasts bond over dumpster dives and rooftop dinners in the theater district. Lyle’s antics also teach Josh’s buttoned-up dad (the ever-dependable character actor Scoot McNairy) how to unleash his inner animal. As Josh’s cookbook-author stepmom, Constance Wu harmonizes with Mendes on “Rip Up the Recipe” to deliver a toe-tapping groove about learning to let loose.

Directors Will Speck and Josh Gordon strike a balance between earnestness and absurdity without getting lost in self-parody. It becomes clear what kind of movie we’re watching early on, when Mr. Grumps – a downstairs neighbor played by Brett Gelman with gleeful indignation – is introduced by that cartoonish name with deadpan earnestness. Yet there’s still room for meta-humor: As Josh tries to reassure his stepmom that Lyle isn’t violent, he blurts out, “He’s not like that – he wears a scarf.”

Davies’s script relies more on archetypes than on fully realized narrative arcs. But that’s a natural concession for a kid-friendly musical that clocks in at under two hours. And there’s not much that could have been done about the uncanniness of Mendes’s flowing vocals emerging from a crocodile’s angular snout. While the movie builds toward a climax that’s entirely predictable, as Hector reappears with dreams of turning Lyle into a star, its laudable call for compassion should still get through to the little ones.

Along the way, Speck and Gordon show off some filmmaking style, weaving the camera through Manhattan’s streets with whiz-bang proficiency. The directors also keep the laughs coming, thanks in no small part to Mr. Grumps’s fussy cat, a CGI creation that scratches the itch for silly sight gags. And they nod to the source material by having Wu’s character sketch Lyle in Waber’s illustration style. For the most part, though, the filmmakers succeed not by imitating, but by creating something entirely their own.