Yes, Buster will do it, especially first thing in the morning in bed when he first wakes up. But he's been known to do it in the sunshine in the grass too. I love it!
Yes Ace loves to rub his back in the grass when he goes outside. But his normal happy greeting is wiggling enough to shake the house and tail wagging faster than the speed of sound
Every now and then he will get on his back! it's definitely not his favorite position to be in though...kinda confused considering I see pictures of bully's on their backs all the time and he really doesn't enjoy it! That is unless he's betting an extreme belly rub!