Sirius/Theo.
Sirius gave Theodore the thumbs up in acknowledgement. As far as Sirius was concerned, Theodore was going to be a mate of sorts now, and a useful one at that—he would, of course, message him to talk again.
His eyes stayed on the other bloke until he was out of sight. It seemed a mistake to him, being alone on Christmas, but it was Nott's mistake to make. Besides, Theodore was clearly much more self-possessed than Sirius himself was; if it'd been his bloke, he wouldn't have handled it nearly so calmly. If he needed to process in silence, that was his dues.
Next, Sirius looked over to see where Theodore's bloke had gotten off to. He watched the blue gentleman (who, fair play to him, looked faintly shell-shocked) get caught up by a short, gregarious man with the goatee. Plain to see that none of it was malicious in the least, but that didn't mean it couldn't hurt.
After a moment's thought, Sirius sauntered over to the table that heaved with Korean BBQ, sweet potato noodles, sweet rice and dried fruits to make up a plate that wasn't Western Christmas food in the least. He added some cutlery and a cup of Sujeonggwa, as well as a whole host of food preservation, anti-tampering and keep-hot charms that he'd had from Andromeda. Just so there was no mistaking who it was for, Sirius charmed a napkin from a festive red to a dark grey and used his wand to write on it his causally elegant hand: For Theodore "It's Already January Somewhere" Nott, courtesy of a very interesting Gryff. Another tap of his wand and it apparated with a light 'pop' to the house he'd noticed Nott had been staying in.
That taken care of, Sirius pocketed some sugar candy for himself and whichever Marauders wanted some, and went looking for James.