When Marvel Comics makes a movie, chances are there will be bonus scenes added, and they normally appear after the credits have rolled. The Avengers will be no different in that respect, but instead of one bonus scene, there are two. One appears midway through the credits and one appears after the credits have completed.
Not only that, but the content of each scene has been revealed. For that, we turn to Topless Robot. Be warned, however there are some major spoilers about to appear, so if you're trying to remain spoiler-free, don't read the next part.
Spoilers ahead, don't read if you don't want to know (you've been warned).
Last chance to look away:
If you stick around through the credits, you're treated to a triumphant scene of Captain America, Thor, Iron Man, Bruce Banner, Black Widow all sitting around a table in a dingy restaurant silently eating together. Essential? No. Exciting? Not particularly. Funny as shit? Very much so.
That's the description for the post-credit scene, which sounds awfully satisfying. The mid-credit scene, however, seems to be setting up future Avengers movies. Again, do not read if you don't want to be spoiled:
Thanos appears after the credits. Apparently Loki gets his Chitauri army from some alien, and that alien has a brief conversation with Thanos as the post-credits stinger, setting up Avengers 2.
If you skipped that part, don't read this next phrase, either: From what it sounds like, future Avengers movies will be dealing directly with the Infinity Gauntlet, which covers a much bigger scope than the current installment does/will, even though what is apparently The Avengers: Part 1 looks like it's tackling some pretty big issues too.
In light of the two bonus scenes revelation, here's every one of the bonus scenes Marvel has introduced in previous movies like Thor, Iron Man, and Captain America, all in one video:
As long as no one else deletes The Avengers, everything should be fine. Just be sure to stick around until the credits are done.