What event led to Liechenstein adding a crown to its flag?

The event that led to Liechtenstein adding a crown to its flag was the 1936 Olympics. Liechtenstein's flag had previously been plain and similar to that of Haiti. However, when the Liechtenstein athletes arrived at the Berlin Olympics, they realized that their flag was identical to the flag of Haiti. In order to avoid confusion, they quickly added a white crown to the top left corner of their flag, giving it a distinct design and making it identifiable as Liechtenstein's national flag.