The Hulk might be known for his incredible strength and rage, but his most impressive power might be his ability to remember what no one else does. On multiple occasions, the Jade Giant has remembered the identities of heroes he was meant to be made to forget. Thanks to his transformation and powers, the Hulk has been able to seemingly do the impossible and not be impacted by the spells made that impact every other hero and villain.
Doctor Strange has cast spells to make the public forget the identities of two heroes, Spider-Man and the Sentry. In the One Moment in Time arc, Peter Parker makes Strange cast a spell to make the world forget his recently revealed secret identity. The comic was loosely adapted in Spider-Man: No Way Home in the Marvel Cinematic Universe. Meanwhile, Marvel's Superman, the Sentry, had everyone's memory (and his own) wiped twice to prevent his dark side, the Void, from breaking free and destroying the Earth. But, in both cases, the Hulk was the only hero who never forgot despite the spells.
The Hulk's secret power first appeared after the Sentry's abilities started to re-emerge in Sentry #3 from Marvel Comics by Paul Jenkins and Jae Lee, after making the world forget who he was to protect them from the Void. Despite Doctor Strange previously casting the memory spell on the world, Hulk still remembers his friend. However, only Hulk does, as Bruce Banner has no recollection of the Sentry. It shows his transformation into the Jade Giant wasn't impacted by the spell.
The Hulk shows off the same secret power during Immortal Hulk: Great Power #1 by Tom Taylor and Jorge Molina. The Hulk and Spider-Man share a touching conversation together after a wild adventure in the comic. Hulk surprises Spider-Man by referring him to his fellow hero as Peter, as he explains, "you made everyone forget who you are. Banner forgot. But I don't forget." Much like the Sentry, Banner doesn't have a memory of who the hero really is, but after his transformation into the Hulk, the green monster does.
Considering the Hulk and Banner are basically two beings operating in one body, it makes sense that the strong hero would remember what his human alter-ego doesn't. The spells cast to erase the world's memory of Spider-Man's real identity and the Sentry didn't seem to have any impact on the Jade Giant, despite working on Banner, giving him a secret power that might be more impressive than any other ability he has. Hulk's memory powers mean he'll long remember what most would soon forget - including the real identities of two of Marvel's greatest heroes everyone else had erased.