The Penguin Secret Agency was a clan from 2005-2010. It would later be revived in 2017 and is currently active.
The Penguin Secret Agency was first started as the in-game secret agency penguins could join through a pathway. It wasn't soon before it was formed into a clan which would fight against other clans and engage in snowball fights. The PSA would deplete in 2010. It would return in 2017 in Club Penguin Rewritten. It being a clan is still a mystery, but is highly likely.
It's first signs of combats were the basic snowball fights all over Club Penguin. It is unknown if they took part in the Color Wars, but it is certain about World War II. After WWII, the clan's size would drop extremely and people would move on. It is possible in World War IV the clan saw action.