The opening scene of Hawkeye featured a flashback to the events of The Avengers in 2012 where we saw a young Kate Bishop witness the Chitauri invasion as they are wreaking havoc among New York City and then Hawkeye inadvertently saved her which lead to her aspiring to take archery and become a hero. It was one of the coolest moments in the series, but as it turns out, there was another Avenger who appeared in the scene that we actually missed.
In an interview with before & afters, Hawkeye VFX supervisor Vincent Papaix revealed that there is a secret cameo of an Avenger during the opening scene of the series that we haven't spotted yet. "Marvel was saying, ‘Can we include Iron Man? Can we have people from Avengers?’ We managed to actually hide one Avenger that nobody has found yet," he teased. "I won’t tell you where it is in there, but there is one Avenger somewhere in episode one."
Afterward, The Direct rewatched the opening scene of Hawkeye again to see which Avenger made a secret cameo that we haven't spotted up to that point. During the moment when Kate was standing in a gaping hole in her apartment's living room and looking at the battle damages, they noticed that we can see Hulk leaping up through the air on a building near the Avengers tower on the left.
You can check the screenshot below courtesy of The Direct:
When The Direct reached out to Papaix about what they spotted, he confirmed that it was indeed Hulk who made his secret cameo in the opening scene. "It is indeed Hulk jumping from building to building and getting a blast from a Chitauri weapon," he told the outlet.
It is awesome to hear that Hulk made a small cameo in the opening scene of Hawkeye which makes a lot of sense since he was in the sequence where the flashback is set and it also adds to the continuity of the franchise. Since you can barely see him during that scene, it would be difficult for the viewers to easily spot it when they watched the episode.
In the end, it's just a fun easter egg for us fans and it's great that they made a decision to add this small detail during the flashback. It's also normal for any MCU films or TV shows to have hidden easter eggs and sometimes not all of us will be able to spot them immediately which is part of the fun. Who knows, there might be more easter eggs in the series that we still haven't noticed.
All episodes of Hawkeye are streaming on Disney+.