It’s easy to forget that, before it became the go-to franchise model for everything from DC to classic horror movie monsters to Ghostbusters, "The Avengers" didn’t sound like a particularly good idea.

Sure, financially it was essentially a license to print money and sell oxygen. But as an actual movie? The idea of cramming all of these characters, arcs and subplots into a single behemoth – under the watch of a primarily TV director with a lone under-performing feature on his big screen helmer resume, no less – was the cinematic equivalent of the first day of college living on your own and celebrating your freedom by binging on all of the junk food your parents wouldn’t allow … and then regretfully upchucking the overload later that night.

Yet Marvel and Joss Whedon’s gummy worm marshmallow Oreo chocolate chip cookie dough ice cream sundae was not only digestible, but delicious – a pile of excess smoothly and savvily honed into a fun, witty burst of pure pop entertainment at its finest. "Guardians of the Galaxy" may be Marvel’s most consistently strong film, but no Marvel entries – and few recent blockbusters period – have reached the ecstatic, cheer-earning highs of "The Avengers."

So, of course, after impressively and effortlessly pulling off that juggling act, "The Avengers: Age of Ultron" adds even more balls, spinning plates and flaming chainsaws to the show. There’s the thus far resoundingly successful Phase Two to be wrapped up, Phase Three to be teased, new characters to add, old characters to enrich, old threads to wrap up, new ones to pull on, shiny glowing MacGuffins to snag … and occasionally even a bad guy to fight if there’s time (probably while a giant object comes crashing to Earth, which – mild spoiler alert – yup).

Amazingly, Whedon and company have managed to make it all work yet again, assembling a ton of moving parts into another thoroughly entertaining – if not quite as easily harmonious – blockbuster. The film is still a fun, exciting blast – certainly on par with Marvel’s current winning streak. This time, however, underneath all of the clever quips and nifty explosions, you can hear and feel the movie’s growing number of gears straining and grinding to work together.

Despite long since finishing their shawarma, "Age of Ultron" opens with the superhero crew still cleaning up the residue from New York City – namely trying to get Loki’s scepter back from a Hydra-corrupted doctor (as seen in the end credits of "Captain America: The Winter Soldier"). After a swiftly directed opening assault – complete with Hulks smashing and Thors hammering – Iron Man (Robert Downey Jr.) nabs the glowing blue trinket.

Still haunted by New York and the potential of a future attack, however, Stark attempts to hone the staff’s power into his Ultron project – a blanketing A.I. fleet of Iron Men hopefully capable of protecting the planet in their place someday. Captain America (Chris Evans), always wary of those seeking overwhelming power over humanity, firmly rejects the idea, and his worries are quickly proven on point. The stone’s powerful sentient A.I. (voiced with an enjoyable perma-smirk by James Spader) inhabits a robot form and plots the end of The Avengers – and humanity for that matter – with a replicant army.

The path from point A to point B, however, takes several detours and picks up more than a couple hitchhikers, with stops along the way for a bombastic Hulk freak-out, the introduction of two villainous mutant twins – one fast (Aaron Taylor Johnson), one telekinetic (Elizabeth Olson) – from the bad doctor’s research and a field trip out to Hawkeye’s (Jeremy Renner) farm. For starters.

"Age of Ultron" is certainly a crowded pot, but the key ingredients to its predecessor’s wild success are still firmly there. As an action director, Whedon doesn’t have the most personality, but the fight sequences – both mammoth and comparatively less mammoth – are still cleanly captured and thoroughly sprinkled with cool action beats. Captain America backflip chucks a motorcycle and teams up with Thor to thunderblast a polite line of Hydra goons, while Hulk effortlessly tramples through a pesky turret – and that’s just in the opening battle, one that enthusiastically opens with a zippy long take. There’s still a whole Hulk versus Iron Man rumble to viscerally entertain.

Whedon delivers at least one of those snap-worthy moments in almost every action scene, and even though the finale is pulling straight from Marvel’s massive impending danger from the sky playbook (though no portal this time!), the resulting visual is awe-inspiring enough to make it a non-issue. Plus, as almost a middle finger to "Man of Steel," every fight scene overtly makes a point to address the safety of civilians in harm’s way. It’s not only a nifty DC dig, but also a great way to enhance the tension and stakes for a film where most of the main players are contractually obligated to survive.

While Whedon does fine work with the action, the writing and character work is where the superhero movie actually earns its title of super. In fact, the most memorable parts of the film simply involve characters lifting – not even using – a mystical mallet.

Whedon’s playfully witty sense of humor and chirpy dialogue is in peak form, delivering plenty of energetic banter in and out of action sequences. It helps that the cast assembled to deliver it has so much charisma and chemistry together. There’s a party scene at about the one-third mark – just the Avengers laughing, chatting and in some cases flirting – that could’ve gone on for an hour, and I’d have been totally satisfied. As fist-pumpingly satisfying and lovingly rendered the big action beats can be in these Marvel movies, the real secret to their success is that it's simply enjoyable spending time with these characters.

The script knows how to bounce these personalities off one another, for laughs and for drama. As a result, even though the plot swerves into some darker, heavier material – fear, responsibility, the testy relationship between ensuring freedom and ensuring peace, (which will lead to "Captain America: Civil War") – the movie nicely maintains its tonal lightness and humor.

That it manages to keep up its high entertainment factor despite its increasingly bloated story is even more impressive. Unlike part one, though, you can feel Whedon sweating, trying to pack so much into just one screen. There are just so many pieces moving around and getting added to the board. There’s the twins and The Vision and Ultron and there’s some random weapons smuggler (Andy Serkis) and there’s the gems and the scepter and the robots and a new robot body and the Hulkbuster armor and a trip to a special pool and a trip to a farm and … deep breath … it’s just a lot of a lot. It's fitting this film's version of the iconic climactic hero shot from "The Avengers" now simply plays as a lot of amusingly destructive motion. 

It's never exhausting or particularly confusing, but with all of that commotion, it’s no surprise some characters, story beats and emotional moments get lost in the dust cloud. Despite getting his name in the title, Ultron makes surprisingly little impact as the lead villain. His motives are muddled, his CG presence lacks menace, and considering how easily his robot drone selves are destroyed, he’s more pesky than intimidating. Spader’s droll voiceover makes him perhaps the most entertaining personality amongst Marvel’s villainous crop, but other than Loki, that’s a pretty spare crowd (I doubt Thor even remembers who he vanquished in "The Dark World").

Some of the clamoring plot mechanics feel rushed, and though Hawkeye pleasantly moves to the center this time through, other characters feel glaringly sidelined. Thor seems like a non-factor, and while the twins have some fun moments (especially the speedy Quicksilver, impressive considering he’s played by Johnson, a yawn trapped in a human body), there’s little to invest in.

There’s only so much screen time to be passed around, and when the time comes for something really dramatic in the back third of "Age of Ultron," what should hit like Thor’s hammer lands more like a plastic Halloween store replica. The same goes for a final assembling of the second class of Avengers, which ends up feeling exactly like that: the second class, the other folks. There’s promise in each one, but by the end of this film, they’re just cool costumed bystanders.

Make no mistake: Marvel is still on its winning streak. All the new extra weight may make "Age of Ultron" sit lower in the water and cut down its top speed, but thanks to Whedon and the cast, it’s still surprisingly buoyant. The highs aren't quite as high, but they're still very much there. One doesn’t need to look too hard to see past some of the clutter and rediscover the mix of battle swarms and post-battle shawarma that made the first "Avengers" worthy of assembly.