Pam's training a temp named Kathy to fill in for her while she's on maternity leave from her made-up job, and she's fairly easy on the eyes. But Jim isn't about to admit that to Pam, whose confidence in her own attractiveness is at a low ebb. At the same time, Pam isn't about to let him not admit it, to the point where she enlists Dwight to help her uncover the truth. Dwight's methods are, naturally, insane, starting with grabbing Jim's junk and ending with dragging both Halperts to a drugstore so he can subject Jim to a lie detector test Dwight has devised using the free blood-pressure testing machine. Dwight busts Jim as a pathological liar based on how high all the readings were, but Pam realizes Jim has high blood pressure, which of course puts all concerns about Kathy out of her mind. At least until Jim ends up sitting to Kathy for the three months.
Andy calls a midday jam session in the warehouse, and while he, Darryl and Kevin are rocking it, Robert California wanders in. He's not mad; quite the contrary, he goes and gets his harmonica to join in. At first the guys are chuffed at having the CEO in their band, but Robert's tendency to walk in and take over extends to the musical realm, as he's invited some ringers who end up pushing our guys out completely. They pretend to be cool about being relegated to lame percussion instruments on the sidelines (including, in Andy's case, his torso) as a tradeoff for getting to jam with the boss, but it soon becomes abundantly clear even to them that they've become superfluous. But they end up having a good time anyway, with a scaled-down jam session out in the parking lot. So it looks like everyone remembers what's really important, then.