This is how I imagine the opening chapter of the seventh book. Er – yes….
Snape's Encounter With Big D!
Professor Snape's gaze idly flicked over this year's new recruits, the Sorting Hat having done it's worst. Having heard of the Potions Master's formidable reputation with stragglers, most of the students scuttled towards the doors of the Great Hall, eager to disappear to their respective houses. One of Hogwarts' newest ghosts, however, sensed that there wasn't enough love and understanding in Snape's corner. The apparition strutted up to the glowering man with an exaggerated swagger.
"Yo yo yo homey! The name's Big D, ready to roll, what's up wit' you gangsta'?"
There was a collective gasp from the room as everyone gawped at the ghostly Dumbledore. His dress sense was certainly – er - different to that from his pre-dead days.
Snape did a double-take. "Excuse me?"
"We is chillin' wit' the freshest crew, know what I'm sayin'?"
"What on earth are you talking about?" Snape glared, taking in Dumbledore's casual attire and the large gold 'D' that hung from his neck. "Tuck that shirt in!"
"Big D goes wit' da flow, boi." Lots of vigorous hand movements.
Dark eyebrows knitted together in confusion. "Why are you referring to yourself in the third person?"
"Pshh!" The old dude dismissed the icy stare with another swing of his arm. "Man you gotta stop the hatin', listen to what I'm sayin' I aint playin', so many lies are messin' I'm guessin' - "
Snape was now utterly confounded and retreated several steps. "Why are you speaking in rhyme?" he demanded. "Have you been hexed?" This behaviour was really becoming quite alarming. Big D, however, didn't seem to have registered his question. He was in full flow -
"I'm bringin' the flava, aint here to save ya' - "
"Wait – I have a counter curse!"
Severus withdrew his wand with startling speed, and his target quickly held his hands up in surrender. As did everyone else within a 25 foot radius.
"Yo yo yo don't sweat, my brother!"
Severus raised an eyebrow in disbelief. Brother? He wasn't aware that he had any siblings – WAIT - was Dumbledore being cheeky? "ENOUGH!" he roared.
"Maaaaaaaan! I aint feelin' it bro'!"
Bro'? Snape had had enough. He didn't care if this was his superior. "Headmaster's office," he snarled, out of habit. "NOW!" Then he realised he was talking to the Headmaster. He was momentarily floundered.
"Woah!" the old homeboy protested, gesturing wildly. "We aint never gonna - "
Too late, Severus had already turned on his heel and exited the hall with a whoosh - leaving one old wizard dude feeling very disrespected indeed.