My Grandpa used to sit in a rocking chair. He had a recliner, but didn't use it because it wasn't comfortable for him.
So one night when were were over there, Dad tried putting shims under the recliner feet to change the angle, to see if that would make it better for him. While we were doing that, Grandma was rummaging around in the closet and knocked over a box of marbles.
That is forever stuck in my mind as the night Grandpa was off his rocker and Grandma lost her marbles.