When someone wants to make a ridiculous comparison, between two things that are completely and utterly different, people often suggest that to do so would be like comparing apples and oranges.
It doesn't make any sense, kind of like this picture!
Apples and oranges have a lot in common! Both fruits grow on trees, they have about the same amount of dietary fiber and calories, and they’re found right next to each other in the grocery store! Still, it’s a commonly used expression.
Ex. You can’t compare tennis and baseball, that’s like comparing apples and oranges.
Far more sensibly, when comparing two things so alike that they could be considered identical, people often say it’s like comparing apples to apples.
Ex. Comparing Sherri to Terri is like trying to compare apples to apples.
BTW: The British have a much better analogy. They say chalk and cheese.