Meaning: crazy or eccentric behavior.
Example: Swerving across three lanes of busy traffic, he must have been navigating with bats in his belfry.
Definition and Origins Source.
- bats in the tower
- squirrels in the attic
- spiders in the crown
- monkeys in the museum
- gremlins in the observatory
Discussion: This is about erratic behavior, so a rewrite should be about erratic-acting animals in tall or stable places.