Marvel Comics have seen no shortage of unlikely couplings, but few have seen a reaction like that of She-Hulk and the Juggernaut. Fans hated the one-time hook-up between hero and villain, and She-Hulk began to canonically deny it had ever happened. The thing is, she turned out to be telling the truth, and the unique manner of how this character detail was retconned became its own entertaining story that brought to attention a double-standard for female superheroes in comics.
In Uncanny X-Men #435 (2004) by Chuck Austen and Ron Garney, Cain Marko was incarcerated and awaiting trial while being questioned by his defense attorney, Jennifer Walters. Later, She-Hulk asks the notorious villain why he prevented fellow prisoner Rhino from escaping and chose to remain in custody. Cain's speech that his opponents rarely take the time to get to know him and his opinions managed to intrigue She-Hulk, creating a connection that led the two to sleep together. Their conversation in bed is interrupted by a rampaging Juggernaut wannabe and his fight with Cain has She-Hulk declare that their hook-up was a mistake.
This moment didn't come up again until Dan Slott's She-Hulk #11 (2005), which saw She-Hulk talking with superhero psychologist Doctor Leonard Samson about the recent changes to her life. After a series of traumatic episodes, Jennifer engaged in a period of heavy partying and unpredictable transformations. When Doc Samson asked if this bout of risk-seeking behavior included sleeping with the Juggernaut, She-Hulk denies that it ever happened and asks why everybody seems to think it did. In She-Hulk #16 (2007), Wolverine likewise references the connection to She-Hulk's bemusement.
It became a matter of public record in She-Hulk #19 , when Jennifer was called to testify during the trial of Samuel Sterns, aka the Leader. Here, a rival lawyer uses the theory that gamma mutates are all different people when not in their human form to try and embarrass Jen, pushing her as to whether she would have slept with a villain like Juggernaut while in human form. Jen denies it happened yet again but the court is presented with legally admissible comic books as evidence to confirm that it indeed happened, much to Jennifer's shame.
In the end, the mystery was solved when Jennifer met an incarcerated She-Hulk from another dimension who was one of many people from an alternate universe taking "holidays" in the main Marvel reality. Jennifer furiously questions this interdimensional tourist and asks her point blank, "Did you sleep with the Juggernaut?" The doppelganger confirms this happily, completing one of the strangest retcons in modern comics.
While the running plotline is mainly played for laughs, Slott also uses it as a commentary on how the world treats Jennifer for the type of liaison that male heroes have all the time. In She-Hulk #17, Jennifer asks Tony Stark how he gets away with sleeping around without consequences, citing that when he does it, they call him a player but when she does it, she gets called a skank. The point is driven even further home when - in a meta moment in the comic - an emergency occurs and Tony is dressed immediately, while She-Hulks spends the rest of the issue fighting in her underwear.
It's debatable whether Slott's retcon of the She-Hulk/Juggernaut hook-up was successful in its aims. While the story draws attention to the double standards applied to male and female protagonists, it never quite escapes them, and She-Hulk is shamed by characters like Wolverine, who embrace the implication that if she did sleep with Juggernaut, she did something wrong. At the same time, Slott focuses on depicting Jennifer Walter's sexual agency with positivity outside this one encounter, establishing the idea that - like Tony Stark - She-Hulk is a pulp adventure hero who regards romantic entanglements as part of the fun of super-heroics.