Not since the glory days of G-Unit has the world so eagerly awaited the release of a mixtape. For this is the identity Marvel's Guardians of the Galaxy series has chosen for itself: It begins as an "Awesome Mix" of rock music from the '60s, '70s, and '80s, and then grafts a space adventure onto them. The original Guardians, in 2014, used that music to announce itself as a different species from the rest of the thoroughbred Marvel stable, a bit shaggier, more playful. It had been a long time since the comic-book movie genre produced anything as fun as Chris Pratt boogying on an alien planet to Redbone's "Come And Get Your Love."

Casual fans remember the specifics of those pop songs, but likely little else, plot-wise. The elusive Infinity Stone, the MacGuffin linking the entire vision board of the Marvel Cinematic Universe together, was involved somehow. But damned if its purpose didn't slither away as writer-director James Gunn thrilled in chasing one bit of irreverence after another, correctly sensing that the only way not to get lost in so much cosmic mythology was to thumb his nose at the whole universe.

The characters, though — well, they stuck out, mostly because of how odd they were. Besides Pratt's goofy, ne'er-do-well rogue Peter Quill, there was Zoe Saldana doused in body paint as tough green warrior Gamora; former professional wrestler Dave Bautista in a charm offensive as sweet purple lunkhead Drax; and the voices of Bradley Cooper and Vin Diesel as, respectively, sarcastic gun-toting raccoon Rocket and lovable tree Groot, who only speaks with three words, one of them his name. With a crew like this, it was fitting the first film included a lineup scene.

Quill's thing is that he was plucked from Earth at a young age by a blue-skinned bandit named Yondu (Michael Rooker), and trained in the art of thieving before he absconded with the ragtag crew who would become the Guardians. The most distinctive part of his Earth backstory was that his mother left him with a Sony Walkman and a mixtape, which became his most prized possessions as he flew through space. At the end of the last film he discovered she'd made him a second mixtape, and honestly, that would have been enough, backstory-wise. But Vol. 2, which is mildly enjoyable while instantly forgettable, makes a gamble that we want to learn even more about Quill's Earth past. It introduces his father, the "small-g god" unimaginatively named Ego (Kurt Russell), who fell for a lovely Earth woman while traveling the cosmos and left behind certain superpower traits in his offspring.

Ego brings the gang to the Eden-like planet that holds his lifeforce and is adorned with his face, a planet he designed from scratch in order to approximate what a perfect world might look like (thereby providing an easy justification for its existence as a giant CGI effect — it's only simulating a real place, after all). There he attempts to sway Quill to do possibly sinister, father-son-god things, which have little to do with whatever overarching story the Marvel Universe is currently trying to tell. "Remember, folks, Thanos is still out there. But first... this!"

There are other plots. The Guardians clash with a race of gold people, an amusing species of rigid, self-important oligarchs who must lay out the red carpet for their empress (Elizabeth Debicki) no matter how gross of a planet she happens to be on. The Ravagers, the band of tooth-decay outlaws Yondu travels with, have exiled him for his sympathy toward Quill; their leader is played by Sylvester Stallone, growling his way through a two-scene role. Gamora's psychotic sister, Nebula (Karen Gillan, also blue), continues to march on the fratricide warpath, hissing and snarling once she gets captured and is forced to listened to the Guardians' bickering. And Groot, who died at the end of the last film with only a seed of himself to survive into a sapling, is now a baby and, in the words of a Ravager, "too adorable to kill."

Like its predecessor, the film's best scene is the opening credits, which foreground Baby Groot dancing to Electric Light Orchestra's "Mr. Blue Sky" while the rest of the Guardians fight a space worm just out of frame. Swapping out yet another giant, ponderous battle for a cute creature and Oldies radio is exactly the sort of action movie send-up the genre needs right now, so it's a shame the rest of the film doesn't follow that same spirit of rule-breaking. Instead, we get straight-laced morals about families that feel like warmed-over Fast and Furious wisdom. The deviousness of the first Guardiansgets delegated to Rocket, whose attempts at crude humor quickly turn irritating; it's as though, nervous that the presence of a talking raccoon would keep adults away, Gunn needed to make sure the cuddly critter got the filthiest lines. (Rocket does get called a "trash panda" at one point, which is a pretty great insult.)

A graduate of the Troma school of gross-out aesthetics, Gunn continues to give his series the most unnerving visual palette in Marvel. Greens, browns, pinks, and blues clash like polyester plaid suits in the same scene, sometimes the same shot. His tableaus can work their B-movie charms: a Ravagers mutiny, where dissenters are ejected into space, is harrowing. But there are other times when the grotesque is just grotesque, as in the climactic battle sequence inside Ego's planet where every corner of the frame is stuffed with murky tie-dye, and we plead for the warm, pleasing color coordination of those totally square Avengers.

"Awesome Mix: Vol. 2" isn't really coordinated, either — it bounces from defiling George Harrison's "My Sweet Lord" to making great use of Fleetwood Mac's "The Chain" — but mixtapes don't require coordination. They're a function of a person's headspace, a way of using tastes in music to forge human bonds. That individuality is why the Guardians soundtrack works while, say, Suicide Squad's upteenth spin of "Bohemian Rhapsody" is so... sigh. Basic. When we feel that we are drowning in a sea of body paint, the tunes can be our signposts, our means of earthly communication with a movie brand that, like Ego, is powerful enough to build its own planet.

As Marvel spreads its seed to more corners of the universe, its offspring no longer has to come with a personality. The Guardians are due to appear in next year's Avengers: Infinity War alongside five jillion other heroes, just more foot soldiers in the onslaught, and their lifeforce is starting to be neutered accordingly. The question will be if we can still hear the music among all the noise.

Copyright 2021 NPR. To see more, visit https://www.npr.org.