5x09 "The One with Ross's Sandwich"

With his second marriage having failed before it began and currently homeless, Ross can feel the stress building up. When his boss eats (and throws away some of) his last Thanksgiving sandwich at work he erupts and earns himself indefinite leave. Joey, still the only person aware of Monica and Chandler's secret relationship, finds himself constantly having to cover for them after Chandler's underwear is found in Monica's apartment and a nude picture of Monica is left in his kitchen but this starts to make him look like a sexual deviant. Joey soon tires of this and looks ready to spill the beans but can't go through with it, instead getting revenge by saying that Monica had slept with him in London and has been stalking him ever since. Phoebe attends literature classes which she wants to learn seriously but Rachel, who accompanies her takes it as nothing more than some fun. The two soon agree that as Phoebe is taking it seriously, Monica should go instead only for her to end up sucking all the fun out of it with her competitive nature.