Time-Traveling Steve
Living in a timeline where you know everything that will happen must be intriguing. That's precisely what Steve Rogers, also known as Captain America, experienced. So, when someone informs Cap that nobody can lift a certain hammer, he already knows who will pick it up.
And that someone is himself, as he does during the climactic showdown in "Endgame." Cap was already well aware of what went down in "Thor," and if he wanted to, he could have strolled over to New Mexico and wielded Mjolnir to prove his worth. That grin, though. That darned grin.
