The Head of Slytherin is Horace Slughorn (who left the role to Severus Snape for fifteen years before taking it up again in 1996) and the House's patron ghost is the Bloody Baron.
Thankfully, Hogwarts' Board of Governors appointed McGonagall as Headmistress after Snape's death, a title which she still holds in the series' current timeline.
Slughorn was the head of house for Slytherin during his time at Hogwarts as Potions Master. His first reign as a professor was around 1935 - 1980. After Dumbledore recruited him for his second stint, Severus Snape was head of house for Slytherin.
Hogwarts is divided into four houses, each bearing the last name of its founder: Godric Gryffindor, Salazar Slytherin, Rowena Ravenclaw and Helga Hufflepuff.
As the prefect of Slytherin and the Head Boy at Hogwarts, Craig Bowker Jr. is ambitious and always trying his best.
We also meet Tom Riddle, who is, as it turns out, the heir of Slytherin. Present only in spirit, he has all the same been controlling Ginny, and having her act as Slytherin's heir.
Minerva McGonagall:
Professor McGonagall is head of Gryffindor house and is the Transfiguration teacher. If you've read Chapter One of Harry Potter and the Philosopher's/Sorcerer's Stone you will know that she can turn into a tabby cat!
The Heir of Ravenclaw was an individual prophesized by the centaur Harmonthrep (Ajrand) to bring honor and glory to the House of Ravenclaw. The Heir of Ravenclaw was in time revealed to be Brian Dumbledore (Ajrand).
Hagrid has mentioned to Harry, in Harry Potter and the Philosopher's Stone, that Harry's father and mother were Head Boy and Head Girl while they were at Hogwarts. While there must be a Head Boy and a Head Girl in each year Harry attends Hogwarts, the only one we ever hear of is Percy.
Pomona Sprout is Professor of Herbology and the Head of Hufflepuff House.
After the Second Wizarding War, Neville Longbottom was known to have taken over the job as Head of Gryffindor.
Head of Ravenclaw house and Hogwarts Charms master, Filius Flitwick taught Hogwarts students the importance of enunciating their spells correctly – although Hermione helped. Exceedingly accomplished at Charms, Professor Flitwick was reportedly also a duelling champion in his youth.
It is definitely easy to miss and the implications are that Slughorn is a possible Death Eater, either in the past or in the present.
Moaning Myrtle
Born in the late 1920s to Muggle parents, Myrtle Warren started her Hogwarts life in the early 1940s, where she was sorted into Ravenclaw. She had no friends, and was bullied relentlessly because of her glasses and acne.
Hedwig's killer is not explicitly identified, so he/she may have appeared in other books, films or video games, but the only known appearance is Harry Potter and the Deathly Hallows and Harry Potter and the Deathly Hallows: Part 1. A popular fan theory based on book canon suggests that Snape may have killed Hedwig.
The Ministry saw the Order as a renegade outfit — ministers were still cagey about Dumbledore possibly wanting their job — so it wouldn't be possible for McGonagall to work for both the Ministry and the Order. McGonagall didn't join the Order of the Phoenix at first because she was spying for the Ministry of Magic.
Young James Potter also did many fine things. When it emerged his close friend Remus Lupin was a werewolf, far from shunning him, he took the extraordinary step of learning to become an Animagus himself. In his later student career he stopped hexing random students in corridors, and indeed went on to become Head Boy.
However, as Hermione went back to complete her education and take her NEWTs, it's likely she was chosen as Head Girl, with her previous record at Hogwarts and everything she had accomplished the year she was helping Harry with his Horcruxes.
Percy Ignatius Weasley is the third son of Arthur and Molly Weasley. He is two years older than the twins Fred and George. He became a Prefect in his fifth year at Hogwarts, which was Harry's first year, and Head Boy in his seventh year. After graduation, he went to work in the Ministry of Magic.
Harry is the magical Heir of Gryffindor (and he's also a descendent of Godric), Neville of Hufflepuff, Hermione of Slytherin and Luna of Ravenclaw.
Credence Isn't Voldemort's Dad But He Could Be Snape's Grandpa. Before Fantastic Beasts and Where to Find Them came out, it seemed like the story's only real Potter connection would be Newt Scamander's relation to Luna Lovegood and a Dumbledore name-drop.
The story of Chamber of Secrets, as you know, is that the Heir of Slytherin has returned and he's out for Mudbloods. The Heir of Slytherin turns out to be Ginny Weasley, who is being controlled via a magical diary that once belonged to Tom Riddle, AKA Voldemort.
At some point in the tenth century, four of the greatest witches and wizards that ever lived founded Hogwarts School of Witchcraft and Wizardry. Their names were Godric Gryffindor, Rowena Ravenclaw, Helga Hufflepuff and Salazar Slytherin.
During school, Penelope was both a Prefect and Head Girl, a title which she shared with Head Boy and her ex-boyfriend Percy Weasley.
Tom was educated at Hogwarts School of Witchcraft and Wizardry from 1938 to 1945, and was Sorted into Slytherin House, a nod to his ancestor Salazar Slytherin himself.