“The Avengers” is not so much a movie as a huge marketing program, one of those pyramid schemes where if you jump on early enough you can actually make money, except in this case, you had to jump on early enough to understand who all the characters are.  Yes, the same can be said of franchises like “Star Wars,” “Harry Potter,” and “Twilight,” but the difference here is that previous, ostensibly stand-alone movies were produced with the inherent goal of creating this behemoth super-hero story.  The two “Iron Man” movies, “Thor,” “Captain America,” and even the series of execrable “Hulk” movies were all designed primarily to introduce this film.            While “The Avengers” fulfills the expectations engendered by those movies, as a singular achievement, it relies exclusively on spectacular special effects.  Almost all character development, and indeed the source of the plot for “The Avengers” was seen in those previous movies—if you missed them (any of them) you have in essence walked in on the middle of the story.  Writers Joss Whedon (“The Cabin in the Woods”) and Zak Penn (“The Incredible Hulk”) are counting on your knowledge of those previous films because the high speed plot of “The Avengers” just does not have the time to fill you in on those basics.  This creates a huge disadvantage for what under other circumstances is a top notch super-hero story with nonstop action and stomach wrenching special effects.            The plot basically has a group of individuals trying to save the world from the dominion of evil.  But first, they must learn how to function as a team, a team known as The Avengers.  The Avengers are pitted against the maniacal and diabolical Loki, reprised by Tom Hiddleston (“War Horse”), Thor’s power-hungry half-brother, who has allied himself with evil aliens who seek the source of power that Captain America’s nemesis Red Skull used to evil effect in that movie.  If you don’t already know those names, well, this movie won’t help.            Robert Downey Jr. (“Sherlock Holmes”) reprises his role of Tony Stark/Iron Man as the only persona Mr. Downey can produce: a self-centered, wise-cracking genius.  Chris Evans (“Push”) recreates his role as Steve Rogers/Captain America: the All-American hero.  Mark Ruffalo (“Date Night”) is brilliantly cast as the tormented scientist Bruce Banner/The Hulk.  Chris Hemsworth (“Star Trek”) returns as the petulantly proud Thor.  Scarlett Johansson (“We Bought a Zoo”) is Natasha Romanoff/Black Widow, a cameo she introduced to us in “Iron Man 2,” an enigmatic assassin who has joined the fight against evil.  Jeremy Renner (“The Hurt Locker”) plays Clint Barton/Hawkeye, the deadliest archer the world has known.  These are The Avengers of the title, and at the end of the movie, you’ll know no more about them than my brief outline, other than that something happened in the past between Natasha and Clint.  Overseeing The Avengers is Nick Fury, Director of SHIELD, a man who seems to barely suppress the rage that is his only companion, played by Samuel L. Jackson (“Pulp Fiction”).If you’re looking for cohesive and intellectually stimulating plot, you won’t find it in “The Avengers.”  If you’re looking for well-rounded characters that grow and develop throughout the movie, presented with Academy Award worthy dialogue and acting, again, you’re in the wrong place.  But, if you want terrific special effects that keep you on the edge of your seat, and costumes and set designs that mimic the original artwork of Jack Kirby.  Those elements, plus some expertly done film editing and superb pacing make this Joss Whedon (“Serenity”) directed film worth watching.  What else would you expect from a pyramid marketing plan?  This isn’t art, after all—it’s business.  And the sales pitch (presentation—look, sets, costumes, special effects), not the product (art—plot, character development), is the key to its success.