Secret InvasionSecret Invasion.

"Secret Invasion" is a comic book crossover storyline written by Brian Michael Bendis and illustrated by Leinil Francis Yu, that ran through a self-titled eight-issue limited series and several tie-in books published by Marvel Comics from April through December 2008. The story involves a subversive, long-term invasion of Earth by the Skrulls, a group of alien shapeshifters who have secretly replaced many superheroes in the Marvel Universe with impostors over a period of years, prior to the overt invasion. Marvel's promotional tagline for the event was "Who do you trust?".