The Sentry once implanted fake memories into the mind of his actual comic book creator, Paul Jenkins, in one of the most meta-storylines in Marvel Comics history. The Sentry is one of the strongest heroes in comics, however, he's also one of the most dangerous. In a New Avengers storyline, it was revealed the Sentry put his own memories into a comic book writer, who wrote stories based on them.
The Sentry originally debuted in his self-titled miniseries, where a man named Bob Reynolds slowly remembered he was once the most powerful hero who ever lived. He originally teamed up with the Avengers but memories of his existence were wiped from reality to repress the evil within him, known as the Void. With the powers of a "million exploding suns," the Sentry's true powers are unrivaled in the Marvel Universe. However, when his evil persona threatened to destroy everything, the Sentry is erased from the entire world's collective memories. The Sentry would return in The New Avengers, where he met his creator, Paul Jenkins.
In New Avengers by Brian Michael Bendis, Steve McNiven, Mark Morales, John Dell, Morry Hollowell & Laura Martin, the Sentry re-emerges, but none of the superteam remembers who he is. As the Avengers try to figure out how to deal with him, Iron Man and Captain America find out he exists in the pages of comic books. Iron Man even introduces him to his real-life creator, Paul Jenkins, who created the character with Jae Lee and Rick Veitch.
Bendis' meta-story is quite confusing, as it's revealed Jenkins (in the comic's universe) was implanted with the Sentry's memories, which made him write the comics based on the hero. The story reveals Sentry's wife, who he believed he accidentally killed, is alive. She ends up meeting Jenkins, where the comic creator is stunned to meet one of his own creations.
The comic version of Jenkins was implanted with the Sentry's real memories so that someone could tell his story and remember him. That means Jenkins thinks he created the Sentry, when his tales were all put in his mind by the powerful hero.
Paul Jenkins was part of the real creative team that created the Sentry and introduced him in the pages of Marvel Comics. However, in the comic's universe, the Sentry found Jenkins and gave him his memories so that his story wouldn't be forgotten - thus, he lived on through his comics. Introducing Jenkins as a character was a bold storytelling decision that helped explain the Sentry and gave him a vessel to store his memories - but by making it his actual comic book creator, it just ended up turning the confusing story into a confusing, overly meta tale.