He liked ice in his champagne.
It was an egregious mistake in the circles of high society, the type of mistake that he wore everywhere he went. Draco watched in awe as the three cubes of ice clinked loudly about with every swirl, drawing the eyes of everyone he schmoozed, everyone he passed, and most notably, the two people he was there to impress.
When Pansy Parkinson and Theodore Nott announced their engagement, Draco took his opportunity to pull him into the hall.
"You can't be serious, Potter!"
"What?"
"Your champagne! It's an insult to the host, who just so happens to be my mother."
He frowned. "How is it an insult?"
"Because . . . well, I'm not sure why, but it is!" Draco wrenched the toasting flute away from him. "Now I'm going to go to the toilet to dump this swill and you're going to go get a new glass. One without ice."
"Fine. But you really ought to try it. It's better cold."
"Excuse me?"
"Try it. Try it with the ice. It's good, I swear."
Draco peeked around the corner. Everyone seemed preoccupied enough with Parkinson's ring, so just to appease Potter, just because it was him, Draco took a small sip.
And from that day on, he took ice in his champagne too.