Jealousy
"Cor, look at he boobs on her!" Sirius shouted and pointed at the TV, not hearing the growl from beside him.
"Oh, yes baby, bend down for me!" he went off again, again missing the even deeper growl of annoyance coming from next to him.
"I'd not hesitate to slither into her chamber of secrets, if you know what I mean," that last one earned Sirius a pillow to the face and a very jealous Hermione leaving the room.
"What did I do? It was only a video of us on holiday together..." he trailed off, looking confused at his girlfriends ill timed jealousy.