The Skrulls are a race of extraterrestrial shapeshifters appearing in American comic books published by Marvel Comics. They first appeared in Fantastic Four #2 and were created by Stan Lee and Jack Kirby. They originated from the planet Skrullos and their empire is located in the Andromeda Galaxy. Their infiltration of Earth was a major event in the Marvel Comics universe as shown in the crossover event Secret Invasion.
The Skrulls posing as different characters as seen on the cover of Secret Invasion: Who Do You Trust? #1 (June 2008). Art by Phil Jimenez
Cover of Fantastic Four vol. 1 #2 vol. (Jan, 1962) Featuring the first appearance of the Skrulls, art by Jack Kirby.
"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?".
Variant cover of Secret Invasion 1 (June 2008), art by Steve McNiven