Tom knows this is Harry Potter's fault
Potter. It was all the Potter boy’s fault. Somehow, after his horcrux was stabbed with a basilisk fang, he wound up here. Over fifty years in the past with pyjamas that were ten sizes too small stretching across his frame. He sat up in this mysterious, grimacing at how the back of his shirt tore and frantically searched for his wand. Tom’s fingers met its hilt and he immediately cast a silent lumos maxima.
First, he noticed that he was in a dorm. The next thing he saw was the tiny faces in the beds next to him. What the hell was he doing in firstie dorms? Someone snored wetly. Disgusting.
You’re in my head! Something screeches. Cockney accent, ugh. Tom hated hearing it.
“Pardon me? This is my head.” Now that he thought about it, though, it did feel more like possession than actually being in a body. It was a good thing he had experience with possession, then.
Nuh-uh! I'm Tom Riddle an' you’ve 'aken over my brain! ge' out!
“I’m Tom Riddle. Pronounce your constants, brat.”
A boy stirred in the bed across from him, and Tom stood and strode from the room. It would not do well for a child to see him in such a state. The things that it would do to his reputation. He shuddered at the thought and quickly transfigured the tattered, threadbare sleep-clothes into something sophisticated. Deep green silk trousers and buttoned shirt. Perfect.
You're no' Tom Riddle! tha's no' possible.
“Unfortunately for you, imposter, it is,” he snapped back in a whisper. The stairs took him into the Slytherin common room. Hm. Odd. He could’ve sworn that the couches had been replaced with velvet covers over the summer before he created the horcrux. Now, they were back to dark brown leather.
A girl around his age with short dark curls sat at a desk, hunched over a parchment. He didn’t recognise her. Tom knew everyone, so why didn’t he know her? His lip curled into a frustrated snarl.
“Excuse me?” he asked politely.
She spun around, putting an elbow on the back of the chair and quickly adjusted her hair. Her appearance was unsalvageable, though, with eye-bags the colour of ash and smudged red lipstick and dark eye make-up. “Um. Hi. I’m sorry, do I know you?”
“I… do not believe we’ve met.”
“Oh… Well, I’m Sylvia Rosier, fifth year.” Oh, good. A pure-blood.
“Tom Riddle. Fifth.”
Her face paled. “That’s not possible. Tom Riddle is the first year mudblood.”
Hey! Don' call me a mudblood!
Tom’s jaw clenched, and he brushed the voice off. The voice of the eleven year old version of himself? Well, damn. That was certainly problematic. “I assure you, I’m not a first year student.”
Sylvia stood, approaching Tom cautiously and squinting at him. “...You look a bit like him. I can see the bone structure… Same nose.” She shrugged. “Did you take an ageing potion, Riddle? It’s an interesting prank, but those things have all sorts of awful side-effects.”
“I didn’t take an ageing potion,” he stepped away from her, “I woke up like this.”
“Oh. You should probably talk to Slughorn in the morning if it doesn’t go away- breakfast is only two hours away.”
“You think that I’m still eleven in my mind, don’t you?” At her shrug, Tom continued, “I’m sixteen. In magic and in mind. Whatever happened, it was not as simple as an ageing potion.”
“Shit,” she swore, then blushed red at her language. “Okay, you really need to talk to Slughorn. What if it’s time travel?”
As disoriented as Tom had been when he woke up, it was beginning to come together. “Time travel… isn’t an impossibility.”
“Oh, great,” Rosier said, high-pitched and sarcastic.
Oh great, indeed.
Are you me from 'he fu'ure?!
Tom didn’t dignify that idiotic question with an answer.