One of the best teachers at Hogwarts School of Witchcraft and Wizardry, Professor Minerva McGonagall is introduced at Four, Privet Drive in the first Harry Potter movie - The Sorcerer's Stone. She also greets Harry's batch from atop Hogwarts stairs and informs the lot that the Sorting Ceremony is to begin shortly.
McGonagall is best described as a disciplinarian. She's stern in her ways and fiercely protective of her students. She hates rule-breaking and tends to insult people with a serious, calm expression. Though the beloved Harry Potter character has a great many quotes to her credit, these, in particular, attest to her ability to deliver sophisticated insults.
"They Are The Worst Sort Of Muggles Imaginable." - Harry Potter and the Sorcerer's Stone
Professor Albus Dumbledore sees McGonagall in her Animagus form, a tabby cat on Four, Privet Drive at the beginning of Harry Potter and the Sorcerer's Stone. McGonagall says she's been observing Harry's aunt and uncle, Petunia and Vernon Dursley all day and thus, is well qualified to form an opinion about them.
Dumbledore is about to drop off infant Harry, and McGonagall urges him to reconsider his decision. She tactfully comments that the Dursleys are the most unpleasant, non-magic family in her opinion. She appears worried as Dumbledore is about to condemn The Boy Who Lived to difficult years at his aunt's place.
"Five Points... Will Be Awarded To Each Of You. For Sheer, Dumb Luck!” - Harry Potter and the Sorcerer's Stone
McGonagall bursts into the girl’s bathroom along with Professor Severus Snape and Professor Quirinus Quirrell after Ron and Harry fend off the mountain troll. McGonagall is taken by surprise and demands the boys explain themselves. At this point, Hermione jumps in and takes the blame. She says she deliberately sought out the troll, leading McGonagall to deduct five points from Gryffindor.
As for Ron and Harry, McGonagall awards each of them with five points not for saving Hermione's life but for being lucky enough to escape the wrath of a fully grown Mountain troll. The quote reflects McGonagall's way of reprimanding the boys and praising their abilities in the same breath.
"Perhaps It Would Be More Useful If I Were To Transfigure Mr. Potter And Yourself Into A Pocket Watch? That Way, One Of You Might Be On Time." - Harry Potter and the Sorcerer's Stone
When Harry and Ron turn up late for their Transfiguration class, the latter heaves a sigh of relief, unaware that the professor is disguised as her cat Animagus. She transforms into a human and proceeds to lecture them.
Ron tries to flatter her, but McGonagall says it'd be more useful if she were to change his or Potter's appearance into a pocket watch, to avoid being late in the future. This quote from Harry Potter and the Sorcerer's Stone is one of McGonagall's sassiest as it combines sarcasm, and excellent timing to convey that she dislikes latecomers.
"Then Perhaps A Map? I Trust You Don't Need One To Find Your Seats." - Harry Potter and the Sorcerer's Stone
In the same scene, Harry tries to explain he and Ron got lost, and McGonagall immediately knows the solution. She says transfiguring them into a map would be more beneficial, as it would help them locate the classroom.
Harry and Ron, who've just seen McGonagall change form, are in awe. They stand utterly dumbfounded and won't dare argue with her or answer back. McGonagall employs more sarcasm to direct the duo to find their seats and heads to the front of the class.
"You see, Honorable As Your Intentions Were, You Too Were Out Of Bed After Hours." - Harry Potter and the Sorcerer's Stone
Only McGonagall can tactfully bring someone's intentions into question, without being blunt about it. When Draco Malfoy reports to McGonagall that he spotted his classmates and rivals, the Trio sneaking around at Hogwarts, she immediately springs into action. She greets Harry, Ron, and Hermione in the corridors, deducts one hundred and fifty points from Gryffindor, and slaps all of them, including Draco with detention.
Surprised, Draco questions McGonagall's sentence, and suggests she made a mistake pronouncing it. The professor says she knows what she's said, as Draco too is guilty of the same mistake. She gives him a cold-eyed stare and orders him to join his classmates in detention.
"But I Must Impress On Both Of You The Seriousness Of What You Have Done. I Will Be Writing To Your Families Tonight, And You Will Both Receive Detention." - Harry Potter and the Chamber of Secrets
When Dobby blocked the entrance to Platform 9 3/4, the duo decided to fly the enchanted Ford Anglia to catch up with Hogwarts Express. Ron, who sat in the driver's seat, turned out to be a bad driver. While they somehow they made it to the school grounds, the car began to break down, and they crashed into the Whomping Willow.
Severus Snape took great offense at Ron and Harry's act, but because they weren't in Slytherin, he couldn't do much except make a case against them. The boys' fates rested in the hands of Professor McGonagall, who saw it fit to write to their families and punish them with detention. While Professor Snape made a fuss, only McGonagall knew the correct way to discipline her students.
"That Wand Needs Replacing, Mr. Weasley." - Harry Potter and the Chamber of Secrets
Since Ron breaks his wand in a collision with the Whomping Willow, it's a bit of a nuisance in the rest of the movie. He makes a fool out of himself in McGonagall's Transfiguration class, when chosen to demonstrate Vera Verto spell. Ron fails to turn Scabbers into a water goblet, and instead turns him into a furry cup with a wriggling rat's tail.
Seeing Ron's massive failure, McGonagall tactfully asks him to replace his faulty wand and continues with her lecture. She doesn't insult Ron's abilities, but rather reminds him to get a new wand.
"Potter, Take Weasley With You, He Looks Far Too Happy Over There." - Harry Potter and the Half-Blood Prince
McGonagall delivers one of the sassiest lines in the sixth Harry Potter movie when she spots Ron and Harry enjoying a free period. She summons Harry and orders him to fill his free time with Professor Horace Slughorn's Potions.
Though Harry understands McGonagall's commands to head to the dungeons straightaway, she doesn't stop there. She orders him to take Ron along as he looks particularly happy, much to her chagrin. While Ron is terrified of Potions, Slughorn promises to sort him out.