"We haven't seen [Hermione] for ages, Professor," Harry went on hurriedly, treading on Ron's foot, "and we thought we'd sneak down to the hospital wing, you know, and tell her the Mandrakes are nearly ready and, er, not to worry —"
Professor McGonagall was still staring at him, and for a moment, Harry thought she was going to explode, but when she spoke, it was in a strangely croaky voice.
"Of course," she said, and Harry, amazed, saw a tear glistening in her beady eye. "Of course, I realize that this has all been hardest on the friends of those who have been…I quite understand. Yes, Potter, of course you may visit Miss Granger. I will inform Professor Binns where you've gone. Tell Madam Pomfrey I have given my permission." (16.59-61)
Remember how the Sorting Hat confirms that Harry would've done well in
Slytherin? Here's a great example. He can be sneaky when he needs to be.
Harry expertly manipulates Professor McGonagall's good nature and her
care for her students. It's really a pretty impressive piece of lying.
So, much of Book 2 is about the ways in which Harry is or isn't
Slytherin. Why is his skill with manipulation not Slytherin here? What makes his lying to Professor McGonagall OK?