Kate's pretty, pretty pigtails
Brothers that make you laugh so hard you cry and remembering all the trouble you used to get into as kids; and then overhearing your mom say, those two made quite the pair when they were younger.
Sister bonding time
Birthday parties for two year olds (and telling the kids I won't be throwing another birthday party for them ever again because of their horrendous behavior the morning of, only to later start planning the boys' birthday party in my head).
Ducks. I will always remember my baby at this exact age whenever I see a duck and it will always make me smile.
My kids doing their homework the minute they get home from school.