Make a bet with them

I began to mix liquids from my bag.

"How about a bet," I said. I could see their eyes grow with interest.

"If I prove Professor Moody to be a fraud," I said nervously, "I want a big wet one planted on my cheek." It was risky, but not too far that it couldn't happen with Hermione. Yet, it also would make them look forward to me being wrong. Padma stared at Hermione, trying to see how she would react. Hermione seemed unhappy with the idea. Yet something happened, Hermione's numbers jumped up.

60% chance to kiss you on the cheek.

I smiled. That had to mean something. It was evidence.

"I'll be ready handsome," said Michael. I winked at him, and he grabbed his glass of water I had gotten them and took a big drink of it. Immediately I began to put my chemistry set away.

"What are you doing," said Hermione? She watched as I packed all of my potions gear away, not understanding why I was putting it up. I held up the pouch that carried the liquid from Moody's flask, and tipped it upside down. Nothing fell out of it. Michael stared at me expressionless.

"Son of an Amazon," said Michael, "you spiked my water didn't you?" I stared at Michael, as everyone realized he was right. It was the toughest few seconds of my life to that point. But when the transformations began, it was clear.

Michael's face widened, as his skin wrinkled and tightened. His voice grew deeper as he cursed me. Until finally Mad Eye Moody emerged. Nobody looked towards us. We all stared in awe at him. And after a few moments of his eye turning every which way, he transformed back.

"He really is an impostor," said Hermione. I could see a difference in the way she looked at me. It was as if suddenly Hermione Granger was respecting me for once.

"Let's go confront him," said Michael.

"That's the stupidest thing I have ever heard," said Padma, "He could be anyone." The three began to argue about the best way to go forward. I let most of it pass as they argued, but one thing stopped me.

"Do nothing," said Hermione, "Harry will be able to handle it." The looks of sickness from the three Ravenclaws stopped Hermione from continuing her statement.

"No," I said, "I will handle it. I have a plan."