Bringing superheroes together might have been a bad idea. All that chest puffing and portentous bluster could suck the oxygen out of the Earth's atmosphere. Thankfully writer-director Joss Whedon keeps things wonderfully bright and breezy, making a long film whizz by faster than a speeding bullet.
This is a Marvel-only party, of course, which is why Superman is a no-show. Iron Man is their biggest hitter - at least in box office terms - and that means Robert Downey Jr is the star of the show. His greatest weapon is his sharp tongue, which he uses to steal scenes like there's no tomorrow. And there mightn't be, because an invasion of Earth is imminent.
Naturally, the egomaniac butts heads with the oh-so-noble Captain America (Chris Evans reprising his 2011 role) who's still a bit stiff after being kept on ice since World War II. Mark Ruffalo is the most subdued of the gang, but he has to be, or else he turns green and smashes stuff up (replacing Ed Norton as Hulk).
Chris Hemsworth returns as that other loveable lunk Thor, a year after his debut outing. It's his bad egg of a brother Loki who is the cause of this little get-together - again played by Tom Hiddleston, who manages the incredible feat of being scary and silly all at the same time.
The end of the world may loom but Whedon creates a good time atmosphere, seeming to take inspiration from old WWII capers like The Dirty Dozen where the fun is as much derived from the rat-a-tat banter between the guys as it is from the big explosions and the butt-kicking.
Scarlett Johansson is drafted in from the Iron Man series to keep the boys in line and Jeremy Renner plays back-up for Loki as the archer Hawkeye (after a brief turn in Thor). She and he have a history in service, but otherwise there isn't too much backstory to slow things down.
Samuel L Jackson is the common denominator in all the above franchises, playing head of the planetary defence league SHIELD. Clearly, this film is part of a bigger campaign by Marvel (it's no accident that Thor and Captain America have closely preceded it), but the superheroes are affectionately portrayed, outweighing any cynicism in the venture.
Pernickety comic book fans may take issue with the light-hearted approach, gaps in logic and a clash of mythologies, but Whedon doesn't patronise viewers. He strikes just the right tone and where there are rough edges, he uses Iron Man's wry humour to smooth them out. The effect is totally disarming.