With The Boys Season 3 confirmed to be adapting the infamous Herogasm miniseries, the show can parody Avengers: Endgame and other crossover films. While the show has taken shots at specific superhero movie franchises before, it has yet to make a direct attack on the pride of the Marvel Cinematic Universe.
Based on the comic of the same name created by writer Garth Ennis and artist Darick Robertson, The Boys offers a twisted take on traditional superhero stories. The series centers around the titular team of anti-superhero vigilantes, who seek to expose the secret crimes of superheroes who use their powers and public image to do whatever they want in private. While the Amazon Prime adaptation utilizes many of the characters from the comics, its storyline has radically diverged from the plot of the source material. It has also gone beyond simply mocking general superhero tropes, as the comic did, to directly satirize specific Hollywood figures and films. Most of The Boys' jokes in this vein have been focused upon Warner Bros. and various DC Comics movies.
Logically this makes sense, as the chief superhero team of the series, The Seven, is a pretty clear parody of the classic Justice League from the comics. The show has also name-dropped both composer Hans Zimmer and writer/director Joss Whedon, while showing clips and movie posters from various works based on Vought-International's superheroes that seem to be aesthetically based on the films of Zack Snyder. However, with Season 3 of The Boys drawing upon the Herogasm storyline from the comics, the show will be able to specifically target Avengers: Endgame.
The opening scenes of Herogasm saw all the superhero teams of The Boys' reality joining together on a mission to travel into deep space, reportedly to confront an alien invasion fleet that threatened all sentient life in their galaxy. The truth was that the entire story was a public relations stunt meant to cover up the fact that Vought-American held a yearly orgy at a private resort so that all of their Supe employees could indulge themselves in secret. The heroes would then "return to Earth" victorious one week later and the comic and film industries devoted to promoting their exploits would have a host of new propaganda material to work with until the next annual orgy when the cycle would repeat itself.
Given that the idea of a shared universe is more heavily associated with Marvel Comics' movies in the public eye, it seems likely that The Boys Season 3 adaptation of Herogasm will target Avengers: Endgame in its satiric efforts. It will be interesting to see which characters The Boys might include in the festivities, as the original comic made reference to shenanigans like a public foursome between the members of its parody of the Fantastic Four. The only certainty is that the adaptation will not include an infamous scene in which Soldier Boy had sex with Homelander, as depicting an act of coitus between Captain America and Superman might be too much, even for a show like The Boys.