Nutty as a fruitcake

Meaning

Used to describe someone who is exceptionally strange, eccentric, or clearly out of their mind. It is a colorful way to question someone's sanity.

Playful, mocking

Used in a sentence

• He wears a tinfoil hat to the grocery store, he is as nutty as a fruitcake.
• I think she is sweet, but she is also as nutty as a fruitcake.
• My grandfather tells the strangest stories, he is as nutty as a fruitcake.