A Basement-Dweller named Jeff becomes obsessed with the Library and, after finding a magical tome, ends up having a "Freaky Friday" Flip with Jenkins. Jeff in Jenkins's body is having the time of his life, being someone important and enjoying the Library's artifacts. Meanwhile, Jenkins has to try to figure out what happened, while being forced to deal with Jeff's mother and D&D friends. Things get worse, when Jeff accidentally unleashes a monstrous creature on the Library.
- Basement-Dweller: Jeff lives in his mother's basement, works at a Geek Squad Expy, and hangs out with his friends, playing Dungeons & Dragons. No wonder he desperately seeks to become someone else!
- Character Focus: The episode is largely focused on Jenkins and him coming to terms with his recent mortality. The others barely get any screen time at all.
- Continuity Nod: Both DOSA and the reporter from "And the Disenchanted Trees" are mentioned by Jeff's friends as part of his obsession with the Library.
- "Freaky Friday" Flip: Jeff uses a Tome of Eldritch Lore to swap places with Jenkins, hoping to escape his Basement-Dweller life. Before going after Asmodeus, Jenkins uses the book to concoct a potion to switch them back.
- Heroic Bastard: Jenkins admits to Jeff's friends that he's Lancelot's illegitimate son, which didn't exactly make him popular at the Round Table.
- Hidden Depths: Jeff and his friends end up being braver than they seem. In fact, Jeff's friends help Jenkins bypass the three traps that allow Jenkins to return to the Annex.
- I Choose to Stay: After stopping Asmodeus, Jenkins finds he's grown fond of Jeff and his friends, so he starts spending his free time in Jeff's basement, becoming their new dungeon master.
- Impaled with Extreme Prejudice: After Jeff distracts Asmodeus, Jenkins manages to impale the Prince of Hell with a sword through the back.
- Let's Get Dangerous!: When Jeff and Jenkins realize that Asmodeus is on his way to Jeff's mother, they dress for combat and grab swords and shields, before heading through the Backdoor.
- Our Demons Are Different: Jeff ends up accidentally summoning Asmodeus, one of the seven Princes of Hell. Asmodeus mostly looks like a grayish orc.
- Out of Character: Jeff couldn't act like Jenkins to save his life, including hitting on Cassandra. Naturally, the others are fairly quickly tipped off that he's not who he appears to be.
- Plot Tailored to the Party: The three trials required to get into the party are tailored to the skills of Jeff's three friends.
- Reality Ensues: Turns out a government organization as large and well-funded as DOSA isn't going to stay secret for long, especially after suffering as embarrassing and expensive a failure as it did in the Season 3 finale; Jeff and the others learn about the Library due to, among other things, files related to DOSA being obtained by Wikileaks.
- This Is Reality: Jenkins constantly corrects Jeff's friends over the "facts" of their D&D book. At the end of the episode, he becomes their new dungeon master in order to set the record straight.
- The Three Trials: In order for Jenkins to sneak back into the Library through a secret entrance, he has to get past three trials. He recruits Jeff's three friends to help him. Naturally, each of them ends up having just the right skills necessary for each trial. One instantly recognizes the required jigsaw puzzle shape as that of a dodecahedron (being an avid D&D player). The second uses her DDR skills to bypass a deadly floor with light-up squares. The third remembers telling his children a bedtime story, which inspires Jenkins to get out of a despair trap. Jenkins sends them to Jeff's place after knighting them.
- Tome of Eldritch Lore: The Asmodeus Grimoire is an ancient book of spells, which Jeff purchases online and uses to switch places with Jenkins. Unbeknownst to him, the book eventually summons Asmodeus himself into the mortal world.