This is simply brilliant. I love the pairing so much, and I just want to pinch Peter's cheeks and give (the wonderfully dreadfully named) Mundungus a pat and a pint. Wonderful characterization of all the Marauders, but especially Peter, whose weaknesses are so understandable and sympathetic here.
The dynamic between them is just so delicious in its restraint and tentativeness. PG-13 this may be, but it is hot. This is absolutely wonderful, Mystery Author, and I know I'm going to be re-reading this one many times.