Assume for a moment that Remus and Sirius were friends with Snape at Hogwarts. Now imagine Sirius wasn't shut in Azkaban. It's the start of Harry's third year at Hogwarts school of Witchcraft and Wizardry and there have been two staff changes: Remus Lupin now teaches Defense Against the Dark Arts and Sirius Black has taken the position of Care of Magical Creatures teacher.
You are now going to see the amusing affect that would have on the Welcoming Feast.
I may write more to this (i.e. the backstory or the rather odd year that would ensue) but that will have to wait for another day.
Harry looked around the Great Hall, surveying the Teacher's Table with great interest. Two new teachers - Black and Lupin, both of whom seemed to get on well with Professor Snape. Actually, Harry noted watching the group of three talking rather animatedly, they didn't just get on well, they seemed almost like friends. But that couldn't be right - Harry had always been under the impression that Snape had no friends and suddenly two turn up out of the blue?
Well, you know what they say - teachers can be entirely different outside of school. Clearly Snape was an example of this if his smile was anything to go by.
As the feast continued onto pudding, Harry looked up again to see the three teachers whispering frantically to each other, pointing occasionally in Professor Dumbledore's direction. Said headmaster was talking to Professor McGonagall and thus had his back to them. Tilting his head in curiosity, Harry watched as Professor Black began to draw letters in the air, with Snape and Lupin smirking and muttering encouragement (presumably, Harry couldn't hear over the chatter of students). Snape then also drew some shapes in the air, which caused all three men to laugh.
Oddly enough, it was Dumbledore who left the Great Hall first that evening after dismissing the students to bed.
"I can't believe we did that," Snape said, starring at the back of Dumbledore's head as the man walked past the Teacher's Table, the words 'I' and 'Voldemort' with a heart in between cut carefully out of the old wizards long white hair.
"We? I only wrote 'Voldemort'!" Sirius hissed as students had also begun noticing their headmaster's new hairdo and were doing their damnedest not to laugh.
"We should probably fix it,," Remus said, always the voice of reason.
"Maybe cut the whole thing off?" Snape suggested.
"What like just there?" Remus said, indicating a line with his fingers. A rather large 'snip' sound echoed through the room, causing everyone to freeze as what looked like a metre of white hair fell to the floor.
"Oh shit," Remus whispered.
Dumbledore stared at the pile of hair in wonder, blinking before slowly reaching a hand back to feel the end of his hair - which was now shoulder length as opposed to waist length. Turning to look at the three ex-students, Dumbledore raised an expectant eyebrow, also reaching out with Legimency.
Upon feeling his mind being probed, Sirius shot up from his seat, loudly proclaiming, "I admit nothing!" before turning on his heel and legging it to the door behind the Teacher's Table, with Snape and Remus quickly following.
"Black you arsehole!" Snape bellowed.
"Wait for us!" Remus yelled, slamming the door behind him and Snape.
The entire hall remained silent for several moments, as though trying to work out what had just happened.
"Well... That's one way to start the year," Harry said blinking dumbfoundedly.