I'm quite certain that this might have happened at a lot of points in the Marauders Era.

Remus was fond of talking about nearly everything he found worthy of his interest that is simply every single thing. He would talk to anyone who would listen about that awesome book he had been reading lately, the strange incident on the Muggle News, the remedy discovered to cure impossible diseases and a lot of other stuff.

Usually, when Remus got a bit too carried away talking to another person, Sirius would no doubt feel an unmistakable pang of jealousy. And these were the times when he would do the inevitable: he would jump on Remus's lap, getting his attention completely and would begin talking quite animatedly to him about random stuff making him ignore the other for a few seconds. Or continue his useless rambling until that person is bored to death and would get up himself and leave.

And when the person would be leaving, Sirius would wink with a smirk on his face, happy that he still happens to be the only one who can distract Rem from others completely.