Most WTF dream that had me questioning reality for the next day or so was discovering I had an older sister I never knew. I was helping my parents move house and found some old toys and photos that seemed out of place. My brother identified the owner by name, told me a few stories about her living with them before I was born and while I was a toddler, but stopped when mum & dad showed up to deny the whole thing. It was the first time I'd ever seen my brother get in trouble for anything. I later find out they had those items burned. After doing some investigating on my own, I found out that she left home for unknown reasons, my brother somehow had been in contact with her a few times as a teen, and I was able to use some of those messages to track her down. So I meet her, she seems well put-together and relatively successful, but cold and distant. Then I find out that our parents had told her never to contact me and that I didn't want anything to do with her. The dream took place over several days to a week, but was actually just one night, and it took all I had not to immediately call my brother and ask if this person actually exists (which would be impossible given how old she was, would mean our parents were together at least 10 years before they met).