I dunno if anyone elses little one does this but thinking they might. When I put Christian down on his playmat, playpen or his crib, he's lying vertically. However, if I check on him (let's say he's in his playpen finishing a nap or his crib when I check on him in the morning), he's lying horizontally instead. He's not upset but looks up at me with this toothless grin. On his playmat, he'll eventually work himself around the mat so that he's laying different directions. I always have to smile when this occurs. Does anyone else's little one do this? Was this simply a stage for you and they 'outgrew' it?