Ooh this thread is so funny. I had a fair few oddball teachers but as I only left school in the fairly recent past most teachers were pretty straight edge and wouldn't have got away with things that they could have done a decade or so before.
One RE teacher, who also did pshe lessons with us had a box we could put anonymous questions about sex into and she would answer them in the lesson. Someone had asked what an orgasm felt like, she told us it was like 'when you go over a bump or hill in the car... with your dad'
she also told us, unprompted, that she preferred her husband to bring her a cup of tea in bed than him giving her an orgasm.
We had a history teacher whose lessons purely consisted of us getting the school laptops to play on while we watched historical dramas, roots and blackadder, two whole years of no actual teaching but we obviously loved it and we were all devastated when he was fired.
Our English teacher in sixth form allowed us to submit homework in cake form, so if you couldn't be bothered to do an essay on King Lear you could instead make and bring in a cake decorated with eyeballs, a jesters hat and storm clouds for example.
We had a maths teacher who was really unfairly strict and gave me more detentions than I can count for things like not having a sharp enough pencil or jiggling your legs under the desk. She was really really obsessed with Winnie the Pooh and would regularly give us work sheets with pooh bear themed questions, and this was at secondary school.
Another maths teacher was a total perv and used to lean in and sniff my friend who wore Britney Spears fantasy perfume if we passed him in the corridor and was constantly telling her how lovely she smelt. He had a picture of his wife and children on his desk but announced to our class that he had bought his girlfriend the Britney perfume for Christmas. He also fully grabbed my arse and pushed me off a bench during a teacher vs pupil charity benchball game.
Our headmistress was a real character and always got dressed up for our end of year plays where the teachers and leavers made up new lyrics to popular songs etc and really got into the spirit of it, she was lady gaga one year which was amazing. She also used to tell us about her 'French dog' and 'American husband' never described them without the nationality first, and we imagined she had multiple dogs/husbands of other nationalities she didn't mention. She used to do a little afternoon tea with champagne and cakes each month for the girls that turned 18. They put a stop to the alcohol after my year though. I bloody loved her she was a great head