The first time it happens Stiles has a mouthful of spring roll slathered in duck sauce and is making grabby hands at Derek. Or rather, at the General Tso's shrimp Derek is holding.
It happens between the moment that Derek rolls his eyes and hands it over, and the moment that Stiles gives him a triumphant smile and takes it. When the muffled "Thanks babe!" comes out Derek and Stiles both freeze. The aftermath of those two little words leave an over whelming silence in their wake broken only by the background noise of Shark Tank.
Interesting fact about Derek, when he blushes it's only at the tip of his ears which incidentally felt like they were two glowing hot coals. Interesting fact about Stiles, when he blushes it starts on his upper chest and works its way up until even his scalp feels hot. Derek knows this because their parents have been friends since before Derek and Stiles were ever a glint in their parent's eyes. Derek has known Stiles since the day the motor mouth was born and Derek has seen Stiles shirtless more than once when they were kids.
Although now that Derek thinks about it, he can't remember ever seeing Stiles with his shirt off since Stiles was in his last year at Beacon Hills Junior High. Derek finds himself thinking about this from his vantage point at one end of the sofa while watching Stiles surreptitiously who was curled up at the other end. This last detail bothers Derek more than he'd like but Stiles is like a weed who takes over everything, occasionally even part of Derek's seat and it bothers him that Stiles isn't doing that now when he was just ten minutes ago.
The silence is finally broken as the end credits run. Derek notices Stiles slight twitch that mirrors his own, he hopes that the awkward moment might be over, but Derek quickly realizes he's sorely mistaken. Derek's werewolf hearing can pick up on the sound of Stiles racing heart, his nose on the smell of Stiles blush. It was making Derek's mouth water, and what the hell was that about? Stiles and he have never been like that! Stiles is like the brother Derek never had, his brother from another mother as Cora delights in saying.
Derek was disappointed once again when a half hour later Stiles gathered up his things and announced he was leaving. Usually reality TV night lasted until late into the night or other times Stiles would spend the night over and they would spend the next day lazing about Derek's loft reading and cooking. But it obviously didn't matter to Derek because five minutes after Stiles announced he was leaving he was out the door without a backwards glance. Derek slowly made his way around his loft cleaning up as he went. The apartment seemed to quite to Derek's sensitive ears as he got ready for bed and he found that his thoughts kept wandering back to Stiles.