Marauders when...
They had found out that you were keeping an illegal magical creature hidden in Hogwarts and they were discussing what to do. You had always been against killing creatures who hadn't done anything wrong so you saved them, much like Newt Scamander. You kept them hidden well until your Hippogriff, Lincoln, got out of your trunk while you helped a unicorn in the forest. Just as they planned on cornering you and demanding you hand them over to the Ministry you wandered into the section of the library they were currently hiding at. Feeling that something was going on you were quick to try and leave.
"Y/n we know about the creatures."
"Oh crap. You can't tell anyone! The ministry will kill them and I've worked so hard into keeping them alive. Merlin there gonna be taken away from me."
"Y/n calm down we won't tell anyone just promise to keep them away from the students."
"I promise I will but that means you four can't scare them when you turn into a stag, dog, wolf and rat."
"You know-."
"I'm a Hufflepuff with a lot of magical creatures I'll know a couple of animagus and werewolf when I see one."
"We'll keep your secret if you keep ours?"
"As long as I get to call you all the nicknames like Padfoot, Moony, Prongs, Wormtail and Mrs Prongs."
"Deal."
"Mrs Prongs?!"
"Thanks, Y/n."
"No problem, Prongs."