There are a few classic sassy Harry moments:
“There’s no need to call me ‘sir,’ Professor.”
You may wear that scar like a crown, Potter, but it is not up to a seventeen-year-old boy to tell me how to do my job! It’s time you learned some respect!“
"It’s time you earned it.” said Harry.
But some of his sass is highly underrated:
“I know what day it is,” Dudley repeated, coming right up to him.
“Well done,” said Harry. “So you’ve finally learned the days of the week.”
“Only you said this morning you would have done it last night so know one could see..I’m not stupid you know!”
“You’re doing a really good impression of it!” Harry snapped.
“Congratulations, Harry!” she said, beaming at him. “I wonder if you could give me a quick word? How you felt facing that dragon? How you feel now, about the fairness of the scoring?”
“Yeah, you can have a word,” said Harry savagely. “Good-bye.”
“Not as stupid as you look, are you, Dud? But I s'pose, if you were, you wouldn’t be able to walk and talk at the same time.”
“An interview?” repeated Umbridge, her voice thinner and higher than ever. “What do you mean?”
“I mean a reporter asked me questions and I answered them,” said Harry.
“This is night, Diddykins. That’s what we call it when it goes all dark like this.”
Yeah? Did he say you look like a pig that’s been taught to walk on its hind legs? ‘Cause that’s not cheek, Dud, that’s true…”
“Wow, I wonder what it’d be like to have a difficult life?” said Harry sarcastically.
“Warrington’s aim’s so pathetic I’d be more worried if he was aiming for the person next to me.”
“Well, I’m terrified now,” said Harry sarcastically. “I s'pose Lord Voldemort’s just a warm-up act compared to you three.” [..]
“You think you’re such a big man, Potter,” said Malfoy, advancing now, Crabbe and Goyle flanking him. “You wait. I’ll have you. You can’t land my father in prison.”
“I thought I just had,” said Harry.
“And they’d love to have me,” said Harry sarcastically. “We’d be best pals if they didn’t keep trying to do me in.”
“Are you out of your mind?” demanded Harry. “A plot to get this house? Are you actually as stupid as you look?”