As hilarious as it is, the "Phineas and Ferb" formula likely wouldn't work in a feature-length film.

So the ever-clever creators of the Disney Channel animated series about two inventive stepbrothers did some modifications for "Phineas and Ferb the Movie: Across the 2nd Dimension."

The relaxed, comfortable story format that fits so well into Phineas and Ferb's 104 days of summer vacation — the boys get an idea; they build something spectacular; their pet platypus turns into a secret agent and foils Dr. Doofenshmirtz; and older sister Candace tries but fails to "bust" them — is not in play here. And with summer vacation now ending, perhaps it's appropriate that the movie ramps up the intensity.

In "Across the 2nd Dimension," worlds collide as Phineas and Ferb crash-land into Doofenshmirtz Evil Incorporated. (If you're hearing the jingle in your head, then you're definitely a fan.) They face real threats, discover their pet's secret identity and meet an otherwordly version of their sister who is a focused, battle-tested soldier.

"But I guess that's life," says Phineas as the movie opens. "One minute you're having the best day ever. The next you're being fed to a monster the size of a two-car garage."

Ferb, of course, doesn't say much, which is consistent with the formula. And if you're wondering whether Mom finds out what the boys were doing the whole time, you'll just have to watch.

This 77-minute movie premiered earlier this month on the Disney Channel and was released on DVD on Aug. 23. It's not the kick-back-and-laugh format that fans of the show are used to, but — like the boys' inventions — it works.

The strengths of the show — subtle, smart dialogue with catchy tunes and quirky lyrics — are all here in mass amounts.

After the movie begins with a shackled Phineas and Ferb marching to their doom, the scene shifts to earlier in the day with a bright, bouncy opening theme song called "Everything's Better With Perry." It's a celebration of the supposedly brainless pet that Phineas and Ferb think "doesn't do much."

The chaos unfolds after Phineas and Ferb build a giant shuttlecock that crashes into Doofenshmirtz's latest invention, the "other dimensionator." The savvy boys get the machine working and open another dimension. Perry, aka Agent P, arrives, but upon seeing the boys — and not wanting to risk being sent to a new "host family" — reverts to his muttering pet state.

Phineas and Ferb end up stepping into another dimension, where they discover other versions of themselves cowering under the rule of a competent, sinister, eye-patched version of Doofenshmirtz. It's a world where everyone wears overalls, there is no summer and "big, scary robots" rule. (The robots actually have two faces, one being that of the pleasant everyman "Norm," who just wants to set up a lunch appointment and make omelets.)

It's also a place where Candace, who wears a belt of hand grenades, has committed her life to protecting her brothers.

The movie reveals how the boys got Perry in the first place, and how the intern Carl played a part. We also learn why the adorably inept Doofenshmirtz has yet to take over the tri-state area.

Packed with creativity, "Across the 2nd Dimension" portrays various worlds that are bizarre, at times creepy and bright enough to give you a headache.

The playlist here is worth a download. (The "Ultimate Fan Pack" comes with a digital copy that allows users to transfer the songs to a portable device, making the $26.99 price a little bit more palatable.) Two particularly good songs are "A Brand New Best Friend (And It's Me)," where the two Doofenshmirtzes become acquainted; and "Summer (Where do we Begin)," where Phineas and Ferb educate their other-dimension counterparts on summer vacation.

Older viewers will appreciate the pop culture references and observations of adult life that kids won't catch. They're everywhere in the script, from Candace dreaming of Jeremy in college wearing tweed jackets with patches on the elbows, to Carl being told, "If you keep up the good work, you'll be an unpaid intern in no time."

There is a trace amount of bathroom humor in the film. It's also somewhat disappointing when Phineas declares that they're going to "kick some robot chassis," an ostensibly innocent phrase that's a little too close to cursing for a kids' show.

Aaron Shill is the editor of features and Mormon Times at the Deseret News.