Updates on the 26th of March happened in 2007, 2009, and 2010.
In 2007 there was one update. The third PSA (Penguin Secret Agency) mission, Case of the Missing Coins, was released! While you can no longer access the PSA HQ, it is still playable on Club Penguin’s fun stuff section.
In 2009 there was a minor update – the chat bubble and chat text were modified to look more clear and readable when speaking to others in game.
In 2010 there were two updates. The first one was the Cupcake Pin being hidden at the Sports Shop (located where the Everyday Phoning Facility resides) and also the igloo music was updated, with the new tracks being Puffle Rescue: Ice Flow, Anchovy Jazz, and Recycle.
Want to see and learn more? Check out these pages about the topics mentioned above.