PAX Australia 2015 - featuring special guest Senator (at the time) Scott Ludlum, this is the one that they ended by putting a bad of holding into another bag of holding, all while knowledgeable audience members shouted not to, and we're all sucked into the resulting tear in the space/time continuum.
From The Beggars Court: a crossover adventure with the Viva La Dirt League's Epic NPC Man, hosted on the official WoTC channel. Set after season 1, DM'ed by Dave. Hing and Alex play their respective characters whilst Ben plays a goblin bard called Jobson Lugnutt.
OK Computer: a standalone short season recorded between Seasons 8 and 9, for podcast release in the first half of 2023.