Hahaha - how cute!
Maybe bubs likes lying on one side more than the other? Check it out next time that you are at your midwife/OB checkup, they will likely have a feel around and see what exactly is going on, but it does sounds interesting.
Do you sleep on one side more than the other? I find that when I sleep on my side, bubs will lie with their back to the lower gravity position. If I roll over in the night, I'm guaranteed to get a baby readjusting.