The story: a bunch of low-level superheroes save the day. This was executed again in the mediocre, direct-to-video "The Specials" as well. But this is the other end of the spectrum: big budget (huge budget, almost $100 Million I think) studio comedy. Yes, the effects are overblown and the huge sets and wonderful production design are a bit much considering the plot. But don't think this as a stupid, special effects-y superhero movie--it's a PARODY. They fight a villain named Cassanova Frankenstein, people. He has a psychofrakulator, whatever that is (it's a doomsday device, he'll take over the world, yada yada.) And resident superhero Captain Amazing (a Zapp Brannigan-esque Greg Kinnear, with commercial-product-logos on his costume, nice touch) is kidnapped. Time for the Mystery Men: Mr. Furious (Ben Stiller, gets mad), The Shoveller (William H. Macy, beats people with shovels), The Blue Raja (Hank Azaria, British, throws forks), The Bowler (Janeane Garafolo, bowls), Invisible Boy (Kel Mitchell, guess what he does), The Spleen (the great Paul Reubens, farts), and The Sphinx (Wes Studi, cuts guns in half with his mind, I am not kidding). The rest of the fantastic cast of character actors includes Geoffrey Rush as Cassanova, Lena Olin heavily edited out as Cassanova's bride, and the one and only Tom Waits as a crazy weapons dealer. So...with Macy, Kinnear, Olin, and Rush there are four Oscar-nominees (and one winner) and Tom freakin' Waits! It's not perfect though. It's overlong and there are some gushes of corniness here and there (The Shoveller's full of them).
The dialogue definitely outweighs the physical comedy, which is sometimes lacking (there's a guy who farts for his power, case closed). The dialogue is definitely a highlight, the cyclical ramblings of the Sphinx, the mixed metaphors of Mr. Furious, etc. It's downright a funny movie, (it will almost make you forget that this was the film that let "All Star" by Smashmouth out into the world.)
Unfortunately, the film did not do as well with critics and audiences as it should have. A sequel was originally planned (the film is in fact based on a comic book and characters from "The Flaming Carrot" comics. The Flaming Carrot was planned for the sequel I believe) but this did not do well at the box office. It could have been a hard sell, a superhero comedy with the guy from "There's Something About Mary." It also could have been the fact that it was released on the same day as "The Sixth Sense"--which ended up being the biggest hit for the month of August--as well as "The Thomas Crown Affair." Two other misunderstood classics were released on the same crowded weekend, oddly enough--"Dick" and "The Iron Giant." Critics gave MM passable reviews, but it was quickly forgotten. Sadly enough, on Comedy Central's Roast of Jerry Stiller, comedian Jeffrey Ross commented to Ben Stiller that, "I saw 'Mystery Men' and I fired MY agent." Ben is then seen to mouth the words, "I should have to." Don't listen to him. Give "Mystery Men" a chance.