Imagine your OTP decorating their Christmas tree together. Person A is extremely picky with decorating, and likes to have it look a certain way, and all person B can do is laugh at person A's behavior and help as much as he/she can, because they think its adorable
Cora entered the library holding a box full of brightly colored Christmas ornaments. She had just come from the main hall where she found her eldest daughter sulking; and after Mary's explanation as to why exactly she was upset, Cora felt she had to do a bit of inquiring.
"Robert?" She called, looking around the library for her husband. Carson had told her that she would find Robert at his desk, but looking around all she saw was Pharaoh lounging by the fireplace. She was just about to turn around and check the drawing room when she heard a muffled "Cora?" in response.
Robert popped his head up from behind the table in the very corner of the room. He looked to be perturbed about something, as a light frown was etched into his brow and his hair was slightly mussed from being under a desk. "What is it, Cora?" He repeated, crossing the room and looking at his wife curiously.
Cora pursed her lips, debating between asking what on Earth he was up to and inquiring about her original issue. She chose the latter; as she was not sure she really wanted to know what he was doing on the floor in the middle of the afternoon. "Robert, Mary tells me you won't allow her to put these colored ornaments on the Christmas tree. Certainly she misunderstood you?"
She could tell by his abashed expression that Mary had misunderstood nothing.
"Well—I did not tell her she couldn't, exactly. I—I simply explained to her the importance of tradition and how at Downton that means every year we use the gold ornaments on the Christmas tree…" He trailed off and focused on a pull in the carpet, brushing at it with the toe of his shoe.
"You told our four year old daughter that she could not put colored ornaments on the tree?" Cora frowned in slight disbelief.
"Cora! The colored ones aren't the ones we always use," he whined. "But now it doesn't matter," he muttered, gesturing with one hand toward the cabinet in the corner. "Usually the ornaments are stored in there, but they are nowhere to be found."
"I had the servants bring them up to the attics last week," Cora answered. She held up a hand to silence her husband, who was just about to protest, and continued, "Robert, they were terribly old and fragile. And more than that, they had hideous little designs on them. I chose these new ones in London because I wanted Mary to be able to help us decorate the tree this year. Will you really deny me and your daughter the pleasure of that?" She looked at him skeptically as he continued to play at the pull in the rug.
"…No…" he murmured in response after a moment.
"What was that?" Cora questioned, holding up the box of new ornaments before him in question.
Robert sighed, his gaze rising from the carpet and back to his wife. "I said no, Cora. I wouldn't dream of standing between you and Mary decorating the tree." And with that, he took the proffered box in one arm and Cora's hand with his other.
He was still not entirely pleased with this new tradition, and knew his mother would have a fit when she found out, but when he saw the utter delight on his daughter's face as she decorated the tree with her parents, he knew it was absolutely worth it.