change one's spots

You're still a young man, the last judge had told him, you still have time to change your spots.

Since the early attack advertising was not working, he tried changing his spots.

No more than cats change their spots, as we say.

But it's hard for a leopard to change its spots.

Every now and then, it seemed, a leopard could change its spots.

McCoy doesn't seem to see a reason to change his spots.

It may be that you are a leopard who can change his spots.

Could it really be possible that the leopard had changed his spots?

And as for Big, I just don't believe he can change his spots.

Can't see them changing their spots - sorry size - any time soon.