It was a most triumphal run, indeed. Sirius was somewhat surprised to find that he had a goodly number of spectators, lined up at various strategic points about the castle, in order to watch him. Some where shyer than others, hiding behind trees or bushes, but others, including some of the girls, were blatantly staring at Sirius' bare physiques.
None of their looks disturbed Sirius in any way. They meant nothing to him, he was basically showing off for their benefit. And because he'd lost the bloody bet with James.
But when he rounded the castle, and was loping along the home stretch, he caught a glimpse of Remus, and for some reason he felt himself pink unexpectedly at the sight, his heart thumping loudly in his chest.
He told it to calm down, as he approached his long time friend. Suddenly, for no apparent reason, as it had been quite quiet and rather pliant for the duration of his run, his cock decided to spring to life. He blushed a bit more. What was up with that?