3. Project Pegasus/42 (The Avengers)
Hardcore comic book aficionados will have likely picked up on this one straight away, but for the rest of us a bit of background knowledge is crucial. During one of the earliest scenes in
The Avengers, agent Phil Coulson comes to recruit Tony Stark for the team, and leaves behind a bundle of files for the billionaire to study, all of which are relating to the destruction of "Project Pegasus," which is destroyed in its entirety during the movie's opening scene. One of the these files is marked "42." So what does this mean, exactly? Well, it's an sly reference to the important comic book storyline know as "Civil War," which forced superheroes into two groups when a new law was passed: those who agreed to reveal their identities to the public, and those who wouldn't (it's far more complex than that, but it'd take all day to explain). "Project 42", though, which this file refers to, was a project developed by Tony Stark which saw him developing an extra-dimensional prison for supervillains. Will this, one day, play a part in the MCU? It'd sure be interesting to see.