The Marvel Cinematic Universe can be an awfully big, noisy and repetitive place to spend your time and money, but at its best, it can also allow for humor, whimsy and lightness of spirit — all qualities that come into play in “Ant-Man,” a winningly modest addition to the ever-expanding Disney/Marvel family. Though we can mourn the more stylish and inventive stand-alone caper we might have gotten from director Edgar Wright (who left the project over creative differences and was replaced by Peyton Reed), this enjoyably off-the-cuff franchise starter takes a cue from its incredible shrinking protagonist (played by a game Paul Rudd) and emerges with a smaller-scaled, bigger-hearted origin story than most comicbook heroes are typically granted. Insofar as it feels like a bit of a tonic next to this summer’s more bloated offerings, this July 17 Stateside release won’t reach the box office heights of the recent “Avengers: Age of Ultron” or last year’s chart-topping “Guardians of the Galaxy.” But worldwide box office should nonetheless prove quite a picnic, aided by 3D showings and solid word of mouth.

Certainly Marvel devotees will swarm to this final entry in what the company has termed “Phase Two” of its ongoing and largely successful plot to colonize the known moviegoing universe. (For those not keeping track, this phase began with “Iron Man 3,” launched “Guardians of the Galaxy” and included the sophomore installments of the Avengers, Thor and Captain America franchises.) That sort of easy integration with the MCU’s bigger, better-known properties seems to be precisely what Wright was trying to avoid with his telling, which he and writing partner Joe Cornish first pitched years ago, well before “Iron Man” kicked off Phase One. And while Wright and Cornish retain story and screenplay credit (the latter shared with the rewriting team of Rudd and Adam McKay), their eventual parting of ways with Marvel stands as a sadly instructive example of what can happen to a talented filmmaker who dares to prioritize personal vision over studio synergy.

Still, whatever has been compromised by turning “Ant-Man” over to the director of “Yes Man,” there’s no denying that Reed’s movie succeeds well enough as a genial diversion and sometimes a delightful one, predicated on the rarely heeded Hollywood wisdom that less really can be more. After a brief 1989-set prologue introducing Dr. Hank Pym (a younger-looking, digitally airbrushed Michael Douglas), a brilliant scientist whose particle research is highly coveted by the forces of S.H.I.E.L.D., the movie settles into a loose-and-casual vibe as it shifts to present-day Northern California, where we first meet Scott Lang (Rudd), a skilled cat burglar who’s just spent three years in San Quentin. He’s picked up by his old cellmate Luis (a scene-stealing Michael Pena), who tries to coax him back into a life of petty crime with his current associates (Tip “T.I.” Harris and David Dastmalchian), but Scott is determined to go straight and reconnect with his young daughter, Cassie (Abby Ryder Fortson). That means paying child support to his disapproving ex, Maggie (Judy Greer), whose cop fiance, Paxton (Bobby Cannavale), doesn’t think much of Scott’s ability to turn over a new leaf.

Paxton has a point, as Scott is soon cracking a giant safe in someone’s basement, where he finds a slightly battered-looking, ’60s-era black suit (the work of costume designer Sammy Sheldon Differ) and soon experiences its properties firsthand: Not only can he shrink to the size of an ant, but thanks to some miracle of atomic compression, he also takes on cannonball strength and bullet speed. As it turns out, both the basement and the suit belong to Hank, who devised his shrinking technology years ago as a powerful U.S. military weapon (as we see advertised in a mock-propaganda film from decades earlier) but ultimately shelved it, lest it fall into enemy hands. Now, however, Hank needs someone able and willing to don the suit again, and he has settled on Scott, whose impressive stealth, agility and talent for thievery are just the skills Ant-Man needs.

The requisite mid-movie training montage (niftily assembled by editors Dan Lebental and Colby Parker Jr.) finds Scott learning not only how to throw a punch and dive through keyholes, but also how to communicate mentally with four different species of ants, entire armies of which will eventually swarm forth to do his bidding. Putting their own spin on a subgenre defined by Jack Arnold’s classic “The Incredible Shrinking Man” (1957) and later popularized by Disney’s “Honey, I Shrunk the Kids” (1989), Reed and his crew deftly orchestrate Ant-Man’s shifts in size and the camera’s subsequent fluctuations in p.o.v. and scale: A splash of water in a bathtub becomes a veritable tsunami, while a Thomas the Tank Engine train set triggers a railroad-hopping chase sequence straight out of an old Western, complete with cutaways that place the action in amusingly tongue-in-cheek perspective.

Less than convinced of Scott’s ability — and thus immediately establishing herself as a promising love interest — is Hank’s combative daughter, Hope (Evangeline Lilly, rocking a pageboy), who would prefer to put on the suit and get the job done herself. That job, it turns out, will require Ant-Man to thwart the schemes of Hank’s ambitious former student, Darren Cross (Corey Stoll), who’s getting dangerously close to replicating his old mentor’s technology in the form of a newfangled shrinking-suit technology called Yellowjacket, with potentially disastrous results for a world still reeling from the cataclysms of “Avengers: Age of Ultron.” As readers of Stan Lee’s comics will know, Dr. Hank Pym himself was a founding member of the Avengers (a fact that goes unmentioned here) and the very first incarnation of Ant-Man, as we see in a brief flashback of him on an airborne mission with his equally shrink-tastic wife, Janet Van Dyne (aka the Wasp).

Janet’s absence in the present day goes some way toward explaining the nature of Hank and Hope’s estrangement, and their complicated father-daughter bond finds an obvious thematic echo in Scott’s determination to do right by Cassie. These connections place “Ant-Man” in a classically Spielbergian world of single parents and broken marriages, where the desire to protect one’s child is a force as potent and primal as anything a mad scientist (or the Hulk) could hope to unleash. In some ways, then, “Ant-Man” feels less like a full-blown superhero spectacular than a goofily amusing, warmly sentimental family drama with a pleasing overlay of blockbuster elements. (It’s telling that this is the rare Marvel extravaganza where a house sustains serious damage rather than an entire city; elsewhere, the film’s most significant location is the Pym family homestead, lovingly mapped out by production designer Shepherd Frankel.)

Some groundwork is laid for future Marvel cross-branding initiatives when Ant-Man must retrieve some crucial hardware from an Avengers base, where he finds himself duking it out with Falcon (the always welcome Anthony Mackie). Beating an opponent, of course, is far less useful than remaining undetected in the first place, and because Ant-Man’s powers are a matter of precision and agility rather than technological ingenuity or brute strength, the movie applies a similar economy and finesse. Notably, the action centerpiece here is not just another bombastic save-the-world confrontation, but rather a heist sequence that finds Ant-Man and his six-legged minions sneaking into Darren’s laboratory. The vibe throughout is playful and unpretentious, from the incorporation of a few upbeat Latin tracks by music supervisor Dave Jordan (with a particularly plot-specific use of “La Cucharacha”) to the film’s nimble yet largely functional visual style, though Reed does pull off one relatively eye-popping, mind-bending sequence that immerses us in the dangerous effects of shrinking to subatomic levels.

The refreshingly (and literally) down-to-earth scale of “Ant-Man” is largely a factor of Rudd’s charming performance as the nicest, most boy-next-door cat burglar imaginable — a most unlikely superhero who, despite his newfound abilities and washboard abs, refuses to take himself or his endeavors too seriously. Happily, the Ant-Man helmet conveniently flips open, allowing us regular access to the scruffy human face behind the red eye-shield and gas-mask-like protrusion (a fittingly ’60s-era touch). Douglas supplies a wonderfully wry presence as a stubborn old father/mentor figure who regards both his daughter and his protege with affectionate exasperation, and Stoll, always a charismatic supporting player, brings a marvelous tech-bro swagger to the role of the villainous Darren/Yellowjacket. John Slattery gets to reprise his “Iron Man 2” performance as Howard Stark in one scene, while Martin Donovan proves suitably sinister in a more extended role as one of Stark’s less trustworthy S.H.I.E.L.D. colleagues.

Yet the most memorable turn here may well come courtesy of Pena’s trusty sidekick Luis; with his aw-shucks grin and his charming habit of telling a story in the most digressive possible fashion, he comes across as one infectiously happy dude who seems thrilled to have stumbled into a superhero movie. “Ant-Man will return,” the film’s second end-credits stinger assures us, and so long as he and his story remain as appealingly human-scaled as they are here, it might be the rare Marvel kicker that legitimately gives us something to look forward to.