On any other podcast, Lars would likely be the "zany" one, but Joe takes the cake in this one. To say that he is an eccentric individual would be quite an understatement. The way he acts on-air, and even in real life, can be incredibly bizarre. He has a strange living situation, has an odd fascination with luggage that borders on sexual, has questionable geographical knowledge, enjoys bizarre fashion combinations, and so on.
Over time, his unusual persona has led Lars to suspect that Joe is actually an alien presenting himself as a human. This culminated on the Quarantine Special episode, in which Lars compared Joe to the protagonist from Poorly Disguised Angel Comics.
Either to add to the joke or to sloppily assuage suspicion, Joe will frequently, and without any prompting, declare on-air, "I'm not an alien!" Lars has compared this to someone introducing themselves at parties, "Hi, I'm Dave; I'm not gay." This would, of course, lead most people to suspect that Dave is gay.
He will also occasionally "slip up" and refer to humans as earthlings, or make a reference to them in a way that implies he is not included in that category.
On Facebook Messenger, Lars has Joe's nickname set to "Poorly Disguised Alien".