Pottermore is an official site filled with extra content about Harry Potter from J.K Rowling. The website launched in 2012 and just went through a redesign recently. J.K Rowling has revealed many exclusive things that we didn't know it it maybe slipped under your nose.
Professor Trelwany had a drinking problem which caused her to be such a bad teacher. Most Harry Potter fans know that Professor Trelwany was actually had the power to see the future but she often invented stupid predictions. In the 6th Harry Potter film Ms. Trelwany seemed to have an addiction to Cherry but according to J.K. Rowling drinking is one of her hobbies and she started consuming drinks because she realised her low status in the Hogwarts staff.
Professor Umbridge was one of the most evil characters in the Harry Potter series and one of the reasons people hate her is because she despises Muggle Borns and people who are not born with pure wizard blood but in fact J.K. Rowling has said that Umbridge's mother was a Muggle and her father was a janitor at the Ministry Of Magic. Her brother was a squibb(someone born into a wizard family but has no magical powers) and Umbridge distanced herself from her family and has remained very bitter ever since.
Professor McGonagall was heartbroken after she graduated from Hogwarts. Minerva McGonagall is known to be the transfiguration teacher and head of Hogwarts house at Hogwarts but in fact at the age of 18 when she returned to her home she fell in love with a Muggle boy. She was head over his heels and she wanted to marry him but she then realised that she could not do so because she would have to lie to him about her being a wizard. She left 3 days later calling off the marriage and leaving him forever.
Neville's parents never recovered. People who have not read the books will know that Neville's parents where tortured by Bellatrix Lestrange. They had to go to Saint. Mungo's Hospital and stayed there. Neville grew up with his grandmother. There was always hope that Neville's parents would recover but I according to Pottermore, they never recovered.