He's got a few screws loose

Meaning

This suggests someone is acting a bit crazy or irrational. It is an affectionate or cautionary way to say their brain is not quite held together properly.

Cautious, judgmental

Used in a sentence

• You should stay away from him, he has a few screws loose.
• That idea sounds like he has a few screws loose.
• I think the neighbor has a few screws loose, he was mowing his lawn at midnight.