Source: comicvine.gamespot.com

6. Secret Invasion

We already know that 2018's Captain Marvel will introduce the Skrulls to the MCU, and that gives us a nice window into 2008’s blockbuster storyline Secret Invasion.

That comic reveals that certain Marvel heroes and villains have been abducted and replaced with Skrull sleeper agents. Then, when that programming breaks down and they reveal themselves, the full-on Skrull battalion visits Earth. They’re accompanied by a platoon of Super Skrulls, each of whom has been gifted with the superpowers of three Marvel heroes.

Revealing that there are Skrull sleeper agents in the Avengers' midst would create a major shake-up. In Winter Soldier, we had a taste of something similar with HYDRA (Sitwell, you bastard), but this would be on a whole "˜nother level. The Skrulls are scary villains with a unique ability to disappear and blend into the background. Their introduction would truly constitute an Avengers-level threat.

Plus, I like their bumpy green chins.