Off your rocker.
[Idiom] OFF YOUR ROCKER. - Understanding the Quirky Off Your Rocker Phrase
Acting crazy.
The phrase "off your rocker" is a playful way to say someone is acting irrationally or is insane. Originating from the image of an old person losing balance on a rocking chair, the expression is commonly used in informal contexts to describe someone's unusual or eccentric behavior.
Example Sentences
He's acting off his rocker.
He's behaving in a very strange or crazy manner.
Running a marathon in that weather? You’re off your rocker.
Running a marathon in such weather conditions seems irrational.
People thought she was off her rocker when she quit her job to travel the world.
People thought she was crazy for quitting her job to travel the world.