The Avengers - Easter Eggs & Hidden Details

The mid-credits scene provides the first-ever glimpse of the MCU's ultimate villain, Thanos. The Other reports to his master about the failed invasion, revealing a greater power pulling the strings. This set the stage for the entire 'Infinity Saga' that would dominate the next decade of MCU films.

The S.H.I.E.L.D. facility where the Tesseract is being studied at the beginning of the film is part of 'Project P.E.G.A.S.U.S.' In the comics, this is a research facility that studies alternative and unusual energy sources, which is a fitting place to be experimenting on the Tesseract.

During the scene on the Helicarrier, Tony Stark is wearing a Black Sabbath t-shirt. This is a nod to the fact that the pioneering heavy metal band is famous for their song titled "Iron Man".

After the Hulk falls from the Helicarrier and reverts to Bruce Banner, he is discovered by a security guard played by veteran actor Harry Dean Stanton. When Banner asks where he is, Stanton asks, "Are you an alien?" This is a fun meta-reference, as Stanton famously starred in the classic 1979 sci-fi horror film Alien.

During the Battle of New York, Black Widow says to Hawkeye, "This is just like Budapest all over again!" to which Hawkeye replies, "You and I remember Budapest very differently." This teases a shared history and a previous mission, which became a long-running inside joke for fans and was later explored in the Black Widow solo film.