"If a classmate falls asleep, I must not take advantage of that and draw a Dark Mark on their arm."

"Moony?" called out two raven-haired boys in unison. They both had huge, mischievous grins plastered on their faces and that could only mean that they were up to no good.

"Yeah?" the sandy-haired boy answered tentatively. His brown eyes grazed over both of them and he knew that he probably shouldn't answer the question that they had in store.

"Okay, well Padfoot nicked this 'thing'," James said as he brought forward an object, "from Lily's bag and we were wondering if you knew what it is?"

Remus took the object from his friend and examined it carefully, a smile creeping across his face. Oh, the trouble that they could cause with this… He debated with himself whether he should tell them what it truly was or not… He decided that it couldn't hurt anything too badly if he told them and, anyways, he could use a good laugh after the test that they had just finished taking. "Guys, this is a permanent marker."

Identical looks of excitement spread across both of the two dark-haired boys' faces. "So, by permanent, you mean, permanent?" asked Sirius.

Remus nodded his head and replied, "It should stay on for a few days. Why? What are you two planning…?"

James jerked his head in the direction of a Slytherin who was taking a nap by the lake. It wasn't just any Slytherin, though, it was Snivellus.

"No…," Lupin told them, half-heartedly, knowing all too well what they were thinking.

Sirius snatched the marker from Remus' hand and uncapped it, holding it an arm's length away from his nose after taking a whiff. "Just watch and laugh," he said with a smirk.

Padfoot made his way towards the sleeping boy, being extremely careful to tip-toe so he didn't wake him. He turned back and gave his fellow Marauders a thumbs-up as he pulled out his wand and muttered a spell that would ensure that Snape didn't wake from his slumber as the prank was executed. Sirius reached forward and a look of disgust crossed his face as he took the Slytherin's left arm in his hand. Padfoot hurriedly traced a shape onto the other boy's forearm and then recapped the marker. "He has been Marked!" he shouted to James and Remus happily.

"Mister Black!"

Sirius' face instantly paled to a ghostly shade of white as he glanced over his shoulder and saw the owner of the stern voice. "Yes, Professor McGonagall…?" He shot her his best "I'm innocent, why are you looking at me?" smile but he knew it was just in vain.

"What is that on Mister Snape's arm?" she questioned, her voice full of anger.

"Well, you see Professor, I was just saving You-Know-Who some trouble and time by Marking Sniv- I mean, Severus myself. I'm just that kind of helpful guy."

"Detention!" barked McGonagall, her face turning a horrible shade of red.

"Yes, Professor."

This was done for Loupyloupowell 's Rule Breaking challenge in HPFC.

Thanks Mew for being a siriusly awesome beta!