There's a subtle connection between Brise and Andrew (the old Reploid from the first three games who told Zero stories), which you won't even notice if you haven't played MMZ3 - or if you've forgotten a certain optional conversation.
Before Mission 15, Brise said... "Yesterday I went walking outside the Settlement and found a four-leaf clover! My grandma used to tell me how four-leaf clovers reminded her of her gentle Reploid teacher..."
That teacher was Andrew. At one point in MMZ3, he said the following...
"A long time ago... I was a teacher at a school... Back then, there were many humans... It is no falsehood to say we lived in harmony together... I have so many good memories of those days... The one I remember most vividly is when we went on a picnic. There was a girl who had forgotten to bring her lunch... And when lunchtime came, she sat alone by herself. All her friends were too busy talking and eating to notice. She hard a hard time fitting in. Didn't speak up much... She didn't know how to tell her friends she forgot lunch. When I saw her, I figured that as much had happened. So I gave her some doughnuts I had made that morning."
"Oh? Bored already? [Yes/No: No] You know, before I taught, I worked at a bread factory. And before that I was a sailor. Oops... Went off track... I was telling you about my giving the girl a doughnut."
"She didn't thank me and ran off with her head bowed... I thought she was going off to be with her friends... But on the way home, The girl got off the bus and gave me something. It was a short letter and a piece of clover. The letter said: "Mr. Andrew, I'm sorry I didn't find you a 4-leaf clover" Written in tiny letters. That was her way of saying "Thank you." Whenever I pass by the harbor where the school was, I recall the sweet voices of children calling to me, "Mr. Andrew"..."