Ei ole kaikki muumit laaksossa

Literally: Not all the Moomins are in the valley

Example: “Hän maalasi autonsa ruudulliseksi; ei ole kaikki muumit laaksossa.” — He painted his car in checks; he has a screw loose.

English equivalent: To have a screw loose

Origin: "Not all the Moomins are in the valley": from Tove Jansson's Moomin books (from 1945), whose family lives in Moomin Valley. The phrase is a modern Finnish way of saying someone is not quite all there, like English "not playing with a full deck." When it was first used is not documented.