A leopard can't change its spots

A leopard can't/doesn't change its spots.

something that you say which means that a person's character, especially if it is bad, will not change, even if they pretend it has I doubt very much that marriage will change Chris for the better. A leopard doesn't change its spots.
See also: change, leopard, spot
References in periodicals archive ?
Their relationship has gone the distance, but, in true Shameless style, prostitute Kelly proved a leopard can't change its spots when she slept with Paddy in exchange for money - when he failed to pull on a night out with his sons a few week's ago.
THEY say a leopard can't change its spots - it seems the same goes for the increasingly bonkers Britney Spears.
With the IRA also withdrawing its offer to put weapons beyond use, it just shows that a leopard can't change its spots and the provos will always return to the bullet and the bomb.
THEY say a leopard can't change its spots and French designer Thierry Mugler showed he is no different.