Black Panther is a remarkable Marvel film because, for once, a standalone film really is just that: a standalone. Unlike films like Captain America: The Winter Soldier and Thor: Ragnarok, one can walk into Black Panther having never seen a single Marvel film, or ever having heard of Iron Man, and never feel lost. Only one scene in the entire film would require explanation, but it comes at the very end of the credit sequence. But unlike some credit bumpers, this one requires a *lot* of explanation. Who is White Wolf? How did Bucky Barnes become a kid favorite in Wakanda? What did Shuri do to him, and what is she teaching him now? Warning: Spoilers for Black Panther follow.
That's not to say that those who are really into the interconnected Marvel-verse won't enjoy this film. The references to the outside story are just subtle, like Shuri referring to Everett Ross as "another" broken white boy for her to fix. (The first obviously being Bucky, left in Wakanda in the Captain America: Civil War mid-credits sequence.)
Those who are obsessed with certain glowing rocks can feel soothed. There are enough glowing stones to go around. And they are obviously what Shuri's been using to help fix her broken white boys.
When we last saw Bucky, he has been put into stasis at his own request in Wakanda, with T'Challa promising Steve Rogers that his friend will be well protected here. Our new post-credit scene follows up. Since then, Bucky has been pulled out of stasis. He's hanging out on the edge of Wakandan territory, in a private spot by the lake, where Shuri has been working on him. Her project may be off to the side, and out of the lab, but it's also not that secret. The children of Wakanda have taken to visiting the weird white-skinned one-armed man, and as Shuri shoos them off, they call out a nickname to him: "White Wolf! White Wolf!"
It's not a dig at his manbunned hair, nor is it that the kids have been watching Game of Thrones again. "White Wolf" is actually a nickname for a white male character who lives in Wakanda already, one that did not turn up in the current Wakandan cast line up, and who Bucky may be filling in for down the road.
In the original comics, "White Wolf" was the nickname given to T'Challa's white-skinned adopted brother, whose real name was Hunter. Hunter's family died in a plane crash that occurred right near the Wakandan border, the boy was the only survivor.
As this was before King T'Chaka had any children, he took pity on the child and ignored advice to let him die of starvation or exposure. Instead, he took Hunter in, adopted the boy, and raised him as his own.
In the early comics, the White Wolf was a foil to Black Panther, the adopted outsider versus the trueborn son and heir, and their sibling rivalry lead to many fights. But both were loyal to their father and to Wakanda. Even after Hunter left Wakanda for good, and became a mercenary after T'Challa became king, if his country needed him, he was always there.
So how does Bucky fit into this role? Well, as we know, he and T'Challa's relationship started off on a bad note, as Barnes, as the brainwashed Winter Soldier was framed for the death of T'Chaka. Bucky is also a mercenary. And finally, as we see from the children, Bucky is slowly being accepted, at least by the younger generation of Wakandans.
The Avengers: Infinity War trailer shows Bucky fighting alongside the Wakandan army. This suggests that the lone white skinned outsider has, despite everything, become accepted into the family.
What does that mean for the future? We'll find out when the next film arrives, but T'Challa may have unwittingly adopted a White Wolf into the family.