Disclaimer: The characters all belong to JK Rowling.
Reason for this? My mind is a scary place. I was out on the boat with my family, armed only with a writing pad and my copy of the Goblet of Fire. I can't find the exact quote, but it mentions that some of the teachers were letting them play games in class and Harry thought Snape would sooner adopt him than let them play games.
After a long and emotional time the jury had given them the results of their discussions and background checks and research: the adoption request had gone through. Severus Snape was now the legal guardian of one Harry Potter.
With joy Harry's left his relative's house, weighted down with his treasured belongings, Hedwig perched happily on his shoulder. From there the two traveled to Snape Manor where Harry was shown his room, taught the house rules and given a tour of said house, not necessarily in that order.
That summer was the best summer Harry had ever experienced. He spent his days exploring the expansive grounds, flying over said grounds and working on homework. Each evening he and Snape would sit down for dinner and conversations about everything under the sun. Needless to say, both looked forward to their conversations.
Near the end of the holidays Harry remembered something. It came during a lull in the chatter and it made him snigger. The sound caught Snape's attention and under relentless prodding, Harry spoke.
"I was just remembering a thought I had in fourth year, Remember when some of the teachers were letting us play games in class around Christmas time?" Snape nodded silently, his face impassive.
"Well, I thought you'd sooner adopt me than let us play games in class," Harry admitted.
Snape arched a thin eyebrow at him but said nothing. However there was a gleam in the older man's eyes that made Harry instantly suspicious.
All good things must come to an end and this holiday was no exception.
The first Friday back at school found Harry seated in the Potions classroom, waiting for his teacher. Five minutes after the bell had gone, Snape stormed into the room, robes billowing in his usual spectular fashion. He stalked up to the front and wheeled around to face the class. His black eyes glinted maliciously and somewhere behind Harry Neville whimpered.
"Welcome back, sixth years," he said silkily. But that was apparently all he had to say on that topic. Absently he flicked his wand at the blackboard. However, instead of rows of instructions, six short, horizontal lines appeared. Around Harry people began to turning to each other and whispering in bewilderment.
When he looked up at Snape Harry saw he was smirking. And Harry knew what that smirk meant: the man was amused at how easily the class was taken off guard.
"Hangman!" Snape announced. "Who will be brave -" and his gaze swept over the class, "and be the first to guess? How about you, Longbottom?"
There was a thud as Neville hit the floor in a dead faint.