Can't (or don't) Judge a Book by Its Cover expression phrase
Said to show that you can't tell what something or someone is like by looking at their appearance only.
A: She doesn't look very intelligent. B: Come on! You can't judge a book by its cover.
My father used to tell me,"Don't judge a book by its cover".
If a person "gets a lot of grief from someone", he or she receives a strong criticism or judgment for something.
Used to say that someone makes a judgment or forms an opinion from something.
The phrase is used since the early half of the twentieth century.
A humorous way of saying that what one has said is just what they acknowledge and may not be entirely accurate
Mike: Have you returned from your vacation on the beach? Your skin seems to get tanned.
Jenny: My skin is always dark. That's my story and I'm sticking to it!