Warning: contains spoilers for Avengers #52!
Marvel’s Captain America is the company’s equivalent of DC’s Superman: patriotic, kind-hearted, fiercely loyal and a bastion of morality among his fellow superheroes. Both will also never hesitate to put themselves in harm’s way to save their friends and civilians from certain death. As such, Captain America is famous for jumping on grenades in the MCU – but the same is true in the comics, in perhaps an even more spectacular fashion.
In the Marvel Cinematic Universe, Steve Rogers is a test subject for Dr. Abraham Erskine’s super-soldier project. Among the other subjects, he’s the most physically weak and sickly by far, possessing a dozen medical conditions that label him as “4F” on Unfit for Service (even during World War II, when America needed every soldier it could get). But during an impromptu test, Colonel Chester Phillips tosses a dummy grenade toward the entire group, and while everyone else runs away from the explosive, Rogers instinctually covers it with his body without a second thought. “He’s still skinny” Phillips says after witnessing the feat.
In Avengers #52, Captain America and Captain Marvel fight dual threats from an alternate universe: the Black Skull (the Red Skull and Venom), and the Ghost Goblin (the Green Goblin and Ghost Rider). The Ghost Goblin’s skull-bombs are imbued with power far beyond the typical explosives used by Norman Osborn, and has already demonstrated as much during the fight. Captain Marvel takes a handful of the tossed items and shouts “This time I’m jumping on the grenade, Steve” as she flies away with the intention of clearing the area before the bombs detonate.
The line implies that Captain America’s MCU feat during boot camp has been officially canonized in the Marvel Comics universe. Furthermore, it’s entirely possible that he’s done this more than once – perhaps even to save Captain Marvel. While Captain Marvel is considerably more powerful than Captain America, the latter is still capable of saving the former’s life; Carol Danvers is supremely powerful, but she is not immortal nor invincible.
Note that in the Marvel Universe, Steve Rogers’ jump persuaded both Abraham Erskine and Chester Philips that the skinny subject was the right man to serve as a human testbed for the Super-Soldier Serum. It’s entirely possible that the same action convinced the top brass in the world of Marvel comics. Regardless, Captain America’s courage is legendary in both versions, and earns his title with his heroic actions.