チョークとチーズ

Idiom:

• They are (like) chalk and cheese

Meaning:

• Very different to each other
• Dissimilar
• No resemblance

Examples:

1. Despite being brothers, they're like chalk and cheese.
2. Ten years ago, Sony and Samsung were like chalk and cheese but these days they're quite similar.
3. Ozzie beef and Kobe beef are like chalk and cheese!