Reveal your Secrets by UmiHoshi on DeviantArt
Artist's comment: When Lupin took the Marauders map for a while from Harry, he must've looked at it a lot, feeling nostalgic.
But just like how Snape got insulted when he tried to unlock the map the wrong way, Lupin can read a few messages from the past (or maybe not entirely?) when he open the map wrong on purpose.
surely, these are insults too. but I guess this was their way of showing their love for each other.
I thought this was a neat concept. You can't see the text of the messages in a thumbnail this size, so I recommend clicking through. Despite not generally being a big Marauders fan I found this rather charming.