Being slightly off one’s trolleyUppermost in my list of top four teaching behaviours is being ever-so-slightly crazy . . . to keep students guessing whether or not I have lost my marbles, and being not quite so predictable.
Behaving in an extremely unusual way or doing something very silly: "Anyone who saw us doing this would think we were off our trolleys." - "Have you gone completely off your trolley? You'll never get away with it!"