Just like how in Friends the group have their sofa in Central Perk, the marauders had their spot with their sofa.
it was a red three-seater sofa which was originally positioned under a big window at the side of the common room, it had an old fashioned charmed megaphone beside it which could play whatever you desired, it was first Remus' spot. He used to sit right in the middle of the sofa alone with a good book and some David Bowie playing in the background.
One night James was looking for Remus as he didn't come down for dinner and he found Remus asleep on this sofa, he didn't want to disturb him, so he moved it with him on it (with magic of course) to be by the big ornate fireplace at the front of the common room, swapped with the main Gryffindor sofa. Then went back to the great hall to finish eating.
When James returned with Peter & Sirius everything was just as James had left it. So the boys carefully sat around a sleeping Remus and decided to play a quiet game of cards.
Since that day that's always been their sofa, no matter where it was positioned.