What does "go bananas" mean — and why is it funny?

informal

Meaning

To become wildly excited, angry, or out of control.

Where it comes from

American slang that spread in the mid-1900s. The link to the fruit is unclear, though it may borrow from older 'banana' slang for a crazy or comic person.

Why it is funny

The humor is the cheerful silliness of the word itself. 'Bananas' is already a faintly comic thing to say, so using it for a loss of control makes even rage sound bright and ridiculous.

Used in a sentence

"The crowd went bananas when the band finally walked on stage."