Wait, who the fuck is this joker?!
What They Left Out:
That joker is Ant-Man, named like that because he has the "power" of shrinking to the size of an ant. Beside him is his assistant/love interest, The Wasp, who also turns tiny but at least gets some wings in return. Ant-Man, on the other hand, has to get around by using exploited ants as skis. I can see why they left him out of the movie: He would have been even less useful than Hawkeye and Black Widow during the big fight scene in New York.
"Hey, where's An- whoops."
Despite being universally recognized as the leader and soul of the team, Captain America doesn't show up until issue #4 ... but the thing is, they don't really need him in the fight against Loki, because Ant-Man saves the day. Actually, that's not accurate: Ant-Man's ants save the day. Just regular ants that he talks to, the way Aquaman talks to aquatic animals. How do the ants save the day? Well, at the end of the comic the heroes think they've got Loki cornered, but he turns himself radioactive and starts killing them (which was a thing he could have done at any point, apparently). The mighty Avengers are completely at the mercy of Loki. The team is over before it even started.
That's when the ants open a trapdoor under Loki, drop him into some sort of furnace, and lock him inside.
While Ant-Man helpfully commentates on what they're already doing.
At this point, Thor probably invited the ants to join the Avengers, but they were too busy ruining someone's cereal, so the team settled for that Ant-Man assclown. Am I being too hard on the little guy? Probably, but I have to make fun of him while I can before Edgar Wright and Paul Rudd make him cool in his upcoming movie (though I should have learned my lesson after my ill-fated 2007 article, "7 Reasons Why Iron Man Is Stupid and No One Likes Him and Never Will").
It Gets Sillier:
Another big difference between the Avengers movie and comic? I'm pretty sure the movie skipped the part where Hulk tries to go incognito and joins a circus masquerading as a robot clown juggling horses and elephants.
"Yes, no one will look at me twice now. I am great at secret identities."