The curse worked so well, they didn't know which side of Snape they wanted to try first. The front or the back. That sanctimonious, pompous Slytherin wasn't so tough now. Not with James holding one side of his body, and Peter the other. In the forest, both put all their weight on his arms and kept Snape's legs apart at the thighs. All he could do was tremble beneath the prodding of Sirius' tongue, as it lapped the length of him and into him. He gurgled helpless sounds of distress, unable to form solid words as Sirius gnawed like a dog and forced Snape's body to vibrate against his will.
Sirius licked, his mass of curls flopping and concealing what he feasted upon at the centermost point of Snape's body. He thought about doing exactly what James wanted. He wanted to. But he was still too human, and all too aware of what it would do to their friendships if they couldn't handle it.
"Do it, Sirius. Don't hold back, make the change. I wanna see this prick squirm."
Sirius couldn't get enough. The animal in him wanted to cover more surface area and to delve deeper. He wanted to make Snape produce the most shameful sounds he could pull from him. His canine instincts were already dominating his reasoning as his mouth salivated excessively, drenching Snape and sucking tender skin between his lips.
If he did it, he mused, it would officially be the worst thing he'd ever done. He trusted his friends with his life, but there was no going back if he let them see the dog version of himself doing this.
If he showed them what they were asking for, he knew they were likely to never look at him the same way again. He wanted to do it. He was going to do it. He risked a glance at Remus, who was no longer admonishing them, but had grown strangely quiet from his position under a tree. Remus stared, transfixed. And judging by the dangerous look in his' eyes, as he let his pack have the meat they wanted, Sirius knew, the wolf in Remus wanted some too.