When my oldest son was about 4, he was given a Lego set that came with instructions. He called them "constructions", which we thought was logical.
My MIL, when waiting for the car in front of her to realize the light had turned green, will say "Pick any color! If you don't like green, pick a different color and go!"
When my youngest son was about 2 and I would do laundry, he would tell me he was "in of pants", as opposed to being out of pants.
My husband calls apartments "compartments".
When I was a child and my dad would get stuck driving behind someone who was going slow, he would often tell me it was an old man sitting on his hat. I never really understood that one, but one day, while driving with my now-17 year old son, I repeated it, and my son laughed so hard he cried.