Go big AND go home. Now the co-chairman and co-CEO of DC Studios for parent company Warner Bros. Discovery, writer-director James Gunn closes out a wholly satisfying trilogy of Marvel Cinematic Universe movies with “Guardians of the Galaxy Vol. 3,” an adventure every bit as heartfelt, uproarious and grand as you would hope and, at this point, expect.

You’ll laugh. You may cry. You’ll probably hold your breath. And you’ll almost certainly think a bit about animal experimentation.

In theaters this week, the follow-up to 2017’s “Guardians of the Galaxy Vol. 2 — and, to be technical, last year’s smile-inducing Disney+ offering “The Guardians of the Galaxy Holiday Special” — primarily is concerned with the long-hinted-at, almost entirely unpleasant backstory of the small-in-stature-large-in-attitude hero Rocket (voiced by Bradley Cooper). Rocket has never liked being referred to as a “raccoon,” but if we needed any proof he once was one, the first image that greets us in the film consists of a group of baby raccoons, adorable as captured by Gunn. We know the future Rocket is one of them.

Gunn then moves us to the present and the Knowhere-based headquarters of the movie’s namesake group of misfit heroes. There, Rocket runs afoul of group leader Peter Quill (Chris Pratt), aka Star-Lord, again attempting to drink away his sorrow over the fact the new version of Gamora (Zoe Saldana) not only doesn’t share his romantic feelings but doesn’t even remember him.

Soon, the Guardians are under attack by the powerful Adam Warlock, the longtime Marvel character finally making his MCU debut, with Will Poulter (“Dopesick”) portraying him. For reasons that will become clear, the powerful member of the Sovereign is there to abduct Rocket, and while he doesn’t succeed, the tough little guy is injured badly in the fight.

To save Rocket’s life, the rest of the Guardians — Peter, Drax (Dave Bautista), Mantis (Pom Klementieff), a settled-in Nebula (Karen Gillan), Kraglin (Sean Gunn, brother of James) and, last but not least, shapeshifting tree-thing Groot (voiced as always by Vin Diesel) — will have to take on the High Evolutionary (Chukwudi Iwuji).

And they’ll need help from Gamora and her new pseudo-family, the Ravagers, led by Stakar Ogord (Sylvester Stallone). Gamora very much gets back in the mix, but, again, this is a different Gamora, one who’s really rough around the edges and doesn’t find any of the oddballs charming, including Peter, who’s doing his best to focus on saving his pal’s life and not on his broken heart.

Just how prickly is Gamora? At one point she frustratingly refers to Mantis and Drax as “Bug and Doofus,” which … doesn’t feel entirely unfair. As they have been since Mantis’ introduction in “Vol. 2” — especially in the aforementioned “Holiday Special” — the over-the-top tandem is good for several memorable moments in this romp, Klementieff (“Uncut Gems”) and Bautista (“Knock at the Cabin”) possessing a little something extra in terms of chemistry in a group with tons of it.

There also are solid scenes with Saldana (“Avatar: The Way of Water”) and Pratt (“Jurassic World Dominion”), and Gillen (“Jumanji: The Next Level”) is able to show a different side of Nebula, which brings something fresh to the formula.

Even as adult Rocket is sidelined for much of the affair, Cooper (“Nightmare Alley”) — with lots of help from the special effects crew — shines as the younger version of the character in a series of impactful flashbacks as he is raised by the High Evolutionary.

Speaking of his highness, he’s so-so as Marvel villains go. However, Iwuji, who plays a key role in Gunn’s “Peacemaker” series, helps keep you interested in this wanna-be god with a performance that offers at least some subtlety.

Like the creatures that the High Evolutionary has altered in his quest for perfection, “Vol. 3” isn’t perfect. Even at about two-and-a-half hours, it packs in so much and tries to shift emotional gears so frequently that it can be a bit dizzying. It is a high-speed train that could run off its tracks at any moment.

But it doesn’t. Gunn is too talented — and surely too invested in this franchise — to let that happen.

As he has done since 2014’s unexpectedly delightful “Guardians of the Galaxy” and including 2021’s R-rated DC Extended Universe blast “The Suicide Squad,” he has made an exceptionally entertaining movie.