Even in my work meetings when we were going around the table introduction ourselves, just one sentence on several comments got my mind a working. In 10 minutes I had a whole story ready to write down.
Sad part is, I forgot to write them down and forgot most of it. Silly thing was, I had a notebook in front of me for taking notes.
Always keep a small notebook with you to write down any thoughts or ideas that pop into your head. Because it's usually the good ones that are forgotten.