"If it's funny, then it should make you laugh," Sirius observed. "Do you feel alright, Remus?" He knew the full moon was close, but since his friend was unaware of the efforts being made to ameliorate those nights for him by the other three marauders, he couldn't very well mention that, since he was not supposed to know Remus' secret - which of course he did.
He laid a solicitous hand upon Remus' arm, gazing at him with concern. Remus was his whole world, whether he realized why or not, and he tended to worry about him.