The author says: The round shaped coins must have a lot of benefits that other figures such as a triangle or a square don’t. Also, non-rounded coins may have many demerits. Aside from those, travelers and other people who are not accustomed to the currency would be able to easily remember how much each of these coins is (as long as she knows how to read pie charts).
In 2005 Taiwanese EVA Airways Corporation and Japanese company Sanrio launched a campaign, creating a "Hello Kitty Jet" using Airbus A330-200. A year later they launched a second Hello Kitty plane. Unfortunately, the company took both of its Hello Kitty jets out of service in December, 2008 and March, 2009. But at least we can see what they used to look like.