I think I managed to avoid spoilers, don't worry!
Fox Mulder: He's around ten years old (yeah his main trauma thing happened at 12, but still he fluctuates around 10) and when he's little it isn't too noticeable unless you know what to look for. He tends to fidget a bit and is scared of bright lights, screaming, and the like. He can be triggered into panic attacks and will hide if he has one, often under a blanket, and has a stuffed fox (because yeah).
He trusts Scully, and she knows about his headspace and will help get him out of situations if he ends up regressing (like if he's actively on a case), she also likes to make him happy by getting ice cream and such. She's not his official mommy, but still fills the role absolutely fine.
(If you're wondering why, it's because in the first episode he mentions he's done regression therapy to access older memories, and he does have trauma from childhood, so I instantly headcanon him as Babie)
