|Date added to the store||Unknown|
|Date removed from the store||Unknown|
Rainbow Penguin was a rejected add-in by iNull (iCyber). It made your penguin flash in every color (from Blue to Arctic White). In the add-in window, you could specify a number which sets how quickly your penguin would flash colours.
The visibility is uncertain, but most likely server-sided. Players found using this add-ins risk getting banned.