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 was reported that in somewhere around 2018, PSA was found to have been active in the Club Penguin Online CPPS. Not much is known about this branch or their leaders, but they had apparently infiltrated numerous armies without notice, and their goal seemed to have been the "avoidance of army monopolies through forced order and constant competition between armies" indicating that they had some sort of secret role to play in atleast one of the wars. No activity has been identified since then, but them still being a clan today is very 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.