off one’s rocker

(idiom) crazy, not thinking properly

Example Sentence:

Mom: If you think I’m going skydiving, you’ve off your rocker.
Son: Come on, mom!
Mom: No way!

If Steven thinks he can go out on a date with the most beautiful woman in school, he’s off his rocker.

From the Blogs:

On the rails and off your rocker

Media:

Similar idioms:

1. got a screw loose
2. not all there
3. drive someone crazy
4. on second thought
5. guts
6. balls
7. you can’t teach an old dog new tricks
8. full of oneself
9. see someone