Warning: contains spoilers for Deadpool: Black, White & Blood #4!
Marvel's Avengers: Endgame is far and away the most successful film in the Marvel Cinematic Universe, garnering widespread positive reviews and a worldwide total of almost three billion dollars at the international box office. The movie granted closure to many Avengers, including Captain America, Black Widow and Iron Man. But the film was not without its flaws, and in Deadpool: Black White & Blood #4, the Merc with a Mouth points out the most glaring mistake that takes place during the final battle.
Deadpool has a long history of breaking the fourth wall in both films and comics. He also has a long history of making fun of Marvel's questionable decisions regarding both Fox's films and the MCU (in his first film outing, he infamously wondered out loud why only Colossus and Negasonic appeared in the mansion, reasoning the studio could only afford so many X-Men). After Disney bought 20th Century Fox assets including Deadpool, he didn't miss a beat in roasting his fellow Avengers regarding Captain America's most famous line in the movie.
In Deadpool: Black, White & Blood #4, Wade Wilson is forced to fight a lawyer-friendly version of the Kool-Aid Man (called Devil Drink Dino in the issue; Deadpool himself even says "You guys are getting so sued"). Deadpool, having already wasted what he considered his best catchphrase while fighting the monster ("Time to go sugar-free!"), decides to rely on an old Marvel standby and shout "Avengers Assemble!" while shooting the monster with a machine gun. However, he's quick to add "But quiet on the 'assemble' part. For extra drama."
Here, Deadpool lampoons what many fans consider to be one of the greatest final battles of the MCU: over 60 Avengers and their allies fighting Thanos and his army in the ruins of the Avengers compound in New York. As a rallying cry, Captain America does indeed say "Avengers assemble" just before the armies charge at one another. But with the hundreds of sorcerers, Wakandans, ravagers and Asgardians assembled, how could anyone reliably hear Steve Rogers' understated and whispered "assemble"? The moment is quickly glossed over in the film, but not fast enough for Deadpool (and plenty of fans) to ignore.
It's admittedly a small moment, but one that left multiple fans scratching their heads. Captain America, while a competent leader, cannot possibly project to the point where an entire army can hear his whispers on a crowded battlefield. Deadpool may not have been in the MCU at that moment, but he saw the same flaw that audiences saw in the theater while viewing Avengers: Endgame.