“The Dirty Dozen.” “The Bad News Bears.” “The A-Team.” “The Expendables.” Stories about a mixed group of badass tough guys who have trouble with authority but learn to work together are second only to stories about loners taking on The Man in their enduring popularity. Writer-director Joss Whedon, who revitalized science fiction and fantasy with “Buffy the Vampire Slayer” and “Firefly” makes “The Avengers” a smart, exciting, and engaging superhero story that deftly balances seven larger-than-life characters (some literally), their personal and inter-personal struggles and their interplanetary battles. The film does not take itself or its characters too seriously but it takes entertainment seriously, serving up plenty of popcorn pleasure.  There’s a light dusting of politics (secret WMDs) and character (sibling rivalry, making peace with oneself), and some humor pixie dust to break the tension and add sparkle, but this is about fighting the bad guys, and it does that very well.

There are two super-geniuses. The enormously wealthy businessman Tony Stark/Iron Man (Robert Downey, Jr.) gets his super-powers mechanically. Scientist/humanitarian Dr. Bruce Banner (newcomer Mark Ruffalo taking over from Eric Bana and Edward Norton) has somehow become credentialed as a medical doctor and is providing health care to the poor while trying to maintain his equilibrium to avoid turning into an enormous green rage monster. There’s a demi-god: the Norse deity Thor (Chris Hemsworth), who swings a mighty hammer. The Black Widow (Scarlett Johansson) is a former Russian spy and assassin. Hawkeye (Jeremy Renner) has super-archery skills, shooting a near-endless supply of high-tech arrows with a Swiss Army knife’s worth of super functions. Super-soldier Captain America (Chris Evans) is still adjusting to modern life after having been frozen for 70 years. For him, defeating the Nazis was just months ago and the discovery that the world is still so unsettled and violent is disturbing.  But he perks up at a flying monkey reference — that one he recognizes.  Nick Fury (Samuel L. Jackson) is the guy with the eye-patch from S.H.I.E.L.D. (Strategic Homeland Intervention, Enforcement and Logistics Division) who brings this group of “remarkable people” together, explaining that they might not be able to save the earth, but they can certainly avenge it. If they can stop fighting with each other in a sort of rock-scissors-paper that has them matching strengths and weaknesses to see whether an immortal deity outranks a guy in an iron suit that flies and which is stronger, the hammer of Asgard or a vibranium shield.

When Thor’s brother Loki (a nicely demented Tom Hiddleston, pale as a vampire) steals the tesseract (a glowing blue cube that has the kind of powers you don’t want in the hands of the wrong people), it is time for the Avengers to assemble. Only the most completist fanboys will think that they could not have cut out about 20-30 minutes of the opening sections of tracking everyone down and having them battle each other until they develop some respect and the ability to work together. Some of it is necessary as an introduction to everyone’s powers and vulnerabilities, but we all know they’re going to get on board, so it slows things down too much.  Do we really need the “This is not a drill” evacuation sequence?  And why must every summer action movie feature a black tie party with a string quartet?

Once everyone is on the team, though, things pick up nicely as Loki’s warriors with long, creepy teeth show up in Manhattan and there is plenty of battle to go around.  The bad guys bring all kinds of nasty stuff, including enormous sea-monster-type flying ships.  And we get to see each of the Avengers do what he or she does best as they struggle with their own issues to be the heroes the world needs them to be.  The Hulk is not the only one who has to make peace with his darker side.  ”Aren’t the stars and stripes a little old-fashioned?” Captain America asks, wondering what his new uniform should look like?  ”People might need a little old-fashioned,” says Agent Phil Coulson (Clark Gregg), who proudly owns a near-mint (light foxing) set of Captain America trading cards.  The idea of heroes sometimes seem a little old-fashioned in these cynical and compromised days, and it is good to see a story that brings that idea back.

NOTE: Stay ALL the way through the credits.  It will be worth it.

DVD/Blu-Ray: There are some lovely extras including commentary by writer-director Joss Whedon, a gag real, and behind the scenes features.

Parents should know that this film has constant comic-book peril and violence, chases, explosions, characters injured and killed, and a brief joke about “weed.”

Family discussion: Why was it so hard for the Avengers to learn to work together?  What was the most important thing they had in common?

If you like this, try: “Iron Man,” “Thor,” “Captain America,” the X-Men movies and the original comic books