What are some things your teachers do that are not funny but are, like, weird?

My History teacher sings A LOT. She used to do singing training (prior to becoming a teacher) so she loves to just randomly sing. Once she was opera singing and it was so loud another student came and shut our classroom door so the noise wouldn't travel. She often tries to just make up stupid songs that are somehow related to the topic we're studying. It's weird, but I think it's also funny.