My mother taught their black lab puppy to sit-up-and-beg. Adorable when he was a puppy. When he grew into his size, he'd still try it, but his barrel-chest made him top-heavy and he'd tip over!
It wasn't fair for such a lovely beastie to be such a goofus!
(Oh - and she fed him gummi bears. Don't do it, you'll never have peace again).