I quite commonly swap between units of measurement part sentance. I switch them around all the time. Just yesterday I was in the hardware store and asked for a piece of aluminium that was 3 inches long, 2cm high and 3mm thick. After I said it I thought to my self "gez, hope he knows what I'm on about".
I used to swap hands I used for playing tennis part way through a game too, when it sutied me, just seemed an obvious optimal way to reach the ball in time.
Perhaps both come from being left-handed, making my brain all muddled up
