My sneaky little guy

When Kade was 8 weeks old he started rolling over from his stomach to his back. We couldn't even give him tummy time because he would flip over the second we set him down. The doctor thought it was amazing especially since he was a preemie. But once he got chunky (around 3 months old) he could no longer flip over. His belly was so fat he couldn't get his legs or feet on the ground for leverage.So everyday I put him on his tummy and try to get him to roll over. I intice him with toys but nothing works. Then yesterday, I set him on his tummy and ran to the kitchen to grab something. To my surprise he was laying on his back when I came back into the room! I have no idea how he did it. I set him back on his tummy and told him to show me what he did but he wouldn't budge. As of this morning he has yet to do it again. He's such a sneaky little guy.