I remember having woken up from a dream where I recognised that a) I'm dreaming and b) It's the same dream I had years ago (a sequel maybe). I can't keep dreaming while being aware that I'm dreaming (supposedly you can train this skill but I haven't) so I woke up.
Obviously I don't remember what the actual dream was, just that I suddenly realised it's a dream from the distant past.
When I was small I used to think about recent dreams while falling asleep, and then I would sometimes have sequels. One memorable dream was where I was taking a walk in the forest with my friend a giant talking cat, and wolves would start chasing us, and we would run so fast that we would start flying. This dream had 2 or 3 sequels that I remember.
Obviously I don't remember what the actual dream was, just that I suddenly realised it's a dream from the distant past.