Club Penguin is a online multiplayer kids games where you walk around as a penguin. Every month they have a party and the first ever party was the Beta Test Party. There were 2 Beta Test Parties which were both only 2 hours long and they both happened on September 21, 2005. At the party the beta testers got the Party Hat (also known as the Beta Hat) which was in the town. The coffee shop had a banner saying "BETA TEST PARTY" and there were 2 boxes full of party hats
At the moment the SWF files for this party have not been found.
UPDATE (4/19/19): Davidsanjuan10 has found the SWF of the Town. Go here: https://web.archive.org/web/20121125123640/http://archives.clubpenguinwiki.info/static/images/archives/b/b2/BetaTestPartyTown.swf
UPDATE (09/03/22): TheActualShow has found all the SWF files on this page: https://cparchives.miraheze.org/wiki/Beta_Test_Party