"When like a car is perfectly balanced so that it doesn't fall of a cliff, a bird lands on the front and makes the car fall of the cliff." While it necessarily happens in cars and in elevator, example can be of dams and such. A example would be Beetlejuice where the husband and the wife survive the crash but then a dog enters and walks on the opposite end of the plank supporting the car and cause the car to fall in water killing the husband and wife.
Hello, Unknown Troper. You'll need to get known to lend a hand here.