I can see Mario one day surprising Peach by showing her every letter she's written to him and watch how emotionally flustered she would get❤️🩷 Peach "You.. you saved all of my letters?🥺" Mario "Of course! See, this is the first one you wrote to me, just as it looked on that day!❤️" Peach "🥺🩷"

I am stealing this headcanon and making it mine.