apples to apples

apples and oranges

A comparison of items that, however categorically similar, is inapt; an incompatible analogy, or the items so compared; a disanalogy.

apples to apples, oranges to oranges

A comparison of items that are similar, while also acknowledging or distinguishing a separation of their sets or categories.

mix apples and oranges

To mix or confuse two completely different objects or ideas.