My earliest memory would be when I was around 3 or 4 years old. I remember watering some flowers on the front porch with my little brother, who was around 1 or 2 then. Because I was taller than him, I could easily spray water over his head as I went from flower to flower. He did not notice the first time, so I kept on watering his head.
I think it is particularly memorable because I found the situation to be funny. I would say that my personality is more or less similar because even to this day, I would pick on my brother (even though he is now much taller than me).
It seems to me that particular feelings not only help something be more memorable, but also makes the person in your memory (you) seem more like yourself, especially when you can relate to those feelings. My earliest memory included hurting my hand on a hot metal slide. It makes the memory more vivid to me and I can also remember several times looking at that slide the next year and remembering how I got hurt and the reluctance to go near the slide.
