Emoticons are plurk advantages than others. For every event, plurk often add a new set of emoticons. However, some emoticons are not available on the emoticon sets. Until now, there are about six hidden emoticons.
Of the six hidden emoticons, there's a bit weird emoticon, Русский. Русский means russian language. I do not know why the emoticon with a picture of a person is spinning, symbolized by a Русский code. Of the six hidden emoticons, there are three emoticons which was launched during the World Cup 2010. In this August, plurk also launched a hidden emoticons. This new emoticon is a picture of people typing on computer. Amix, plurk developer, show this emoticon when he has Merged code from Wedoist.com into http://Todoist.com.
Here is a list of six hidden emoticons plurk
In addition, plurk also just add an emoticon for karma 100, picture of people drinking coffee in front of the computer. However, unfortunately the trick to use emoticons for 100 karma is not working anymore.