chalk and cheese
A phrase used to emphasize that two people or things are very different from one another. Good luck getting those two to talk to each other—they're like chalk and cheese. My daughters are chalk and cheese these days—one loves baseball and the other loves ballet.
(like) ˌchalk and ˈcheese
(also as different as ˌchalk and ˈcheese) (British English, informal) very different: It’s hard to imagine that Mark and John are brothers — they’re like chalk and cheese.chalk and cheese
Two objects that although appearing to be similar are in fact different. Just as certain varieties of crumbly white cheese might at first glance resemble chalk, so for example, siblings who resemble each other might have completely different personalities. They would be said to be as different as chalk and cheese.