With this sheet of self-adhesive stamps, Finland post officially launched the world's first "angry birds" stamps. This set of stamps was personally designed by "angry birds" game developer, Rovio's art director Toni Kysenius. It features six of the popular game characters - five birds and one pig.
Rovio entertainment is a Finland based mobile phone software development company, founded in 2003. In 2009 the company developed the famous touch-screen smart mobile phone game software "angry birds". The game as we all know was a great success, and soon swept the world. The game has been called as "one of the most mainstream games out right now", "one of the great runaway hits of 2010", and "the largest mobile app success the world has seen so far".
There is a pattern on the stamps that is visible only under UV light. Here's the image of the sheet under UV light. What you see now under the light are these little pigs on the corners of each of the stamps.
Also if you look closely, an irregular perforation follows the shape of the characters. The sheet of six 1st class stamps also includes Priority labels fitting the appearance of the stamps.