If the hat fits(, wear it) American British saying negative UK informal ironic
Also US "if the shoe fits (, wear it)".
"If the hat fits (,wear it)" is used in the situation that a description or criticism was made for somebody and they should consider and concede it and take it as a warning.
I don't mean you are unreliable, but if the hat fits...
He knew the person who screwed all things up, but he just talked about his disappointment and told us "If the hat fits, wear it."
He's indeed an easy-going guy, so you should think about why he told you that. Just... if the hat fits.
This idiomatic expression first appeared in the early 16th century, originated from the image of a fool's cap (with the old-fashioned idiom "if tha cap fits, wear it").
If you're off your trolley, your ideas or behaviour are crazy or insane.
You really think whether i'll pay the debt. You're off your trolley