Seamus finally managed to transfigure water into rum in Chapter 12 of Snapped. There were some consequences he hadn't foreseen.
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"Hello Seamus old chap."
Seamus gulped as one of the Weasley twins seated himself on Seamus' left side. He glanced around. Everyone in the common room was studiously looking the other way.
"We've got a nice little proposition for you," the second twin said from his right, and Seamus barely managed to stop himself from jumping.
"We'd like the spell for that water to rum transfiguration you managed at dinner," twin on the left said.
"And in return we'll keep everyone else that's interested off your back," twin on the right said.
"And there's certainly going to be quite a few of us that are interested," they chorused.
The twins were grinning widely, but their eyes shone with barely concealed mischief and the hint of malice that made their jokes hilarious, unless you were on the receiving end.
"And if I don't tell you?" he asked, although he could very well guess the consequences.
"Let's just say."
"We'll make your life."
"A living hell."
From nowhere both the twins' wands had appeared in their hands.
Seamus smiled weakly. "How could I refuse?"
The twins smirked. "We knew you'd see it our way."