So Carol Danvers got an assist from Santa Claus in Captain Marvel #11. It had appeared to be some poor mall Santa Grace Alexander and June Covington abducted to use as a test subject, but then he changed into Real Santa.
Chris Sims had talked about it in a past Ask Chris, how in the Marvel Universe, people seem to absolutely believe and accept that Santa exists, to the point he has his own entry in the Official Handbook of the Marvel Universe. So Carol's complete lack of surprise at his appearance is perfectly natural. Still, it's the nature of him and his form that interests me, because the Mall Santa had a fake beard and looked nothing like ole Saint Nick, right up until he did.
The simplest explanation is that Santa, being able to see and know everything, knew Grace and June were about to be naughty, knew that nice Carol Danvers was their target (and that her friend Tracy could use a pick me up), and assumed another form to be abducted so he could help out. If we factor in that supposedly in the Marvel U. Odin was an inspiration (or early version) of Santa, handing out presents in elation over how Thor killed some troll, it would make sense for Santa to behave that way. Odin has at various times loved to take other appearances to either play tricks on people, or teach his son some life-lesson. So tricking a couple of villains and ensuring they aren't able to harm anyone on Christmas, would be somewhat in character for him.
But there's a part of me that wants to think Santa can possess or swap places with any one of his avatars or servants. Like certain interpretations of Billy Batson and Captain Marvel (the Big Red Cheese one, not Danvers), or a less malevolent version of that Space Phantom guy who hangs out in Limbo. He can keep them from harm that way, or it would be one way to get wherever you needed to be fast.