In a dream: My best friend and I had an insanely brutal fight and I remember how real the dream felt. We both said the most hurtful/personal shit to each other and I absolutely hated this mother fucker (in the dream).
In real life I wake up from said dream. I think nothing of it, go to work, and live out my day.
That night I had another dream, where a completely different friend approached me and asked if I was still fighting with so and so. I remember as I was explaining the situation to them stopping and thinking "WTF, that wasn't real, it was in a dream and how did you know about it?"
It was weird being 100% aware that I was in a dream (as I was dreaming it), knowing that the person in front of me wasn't actually there talking, and reflecting on my actual day IRL (as I was dreaming) to confirm all this. Maybe others have had the same or similar experiences, but I've never had anything like that happen to me (before or since) and it was a pretty eerie/surreal to me.