Dwight has wedged a jack-o-lantern onto his head and successfully scared the crap out of Erin, but now it's stuck. Jim's attempts at assistance are mainly aimed at demonstrating how various implements would damage Dwight's head as much as the pumpkin itself. As we see Dwight going about the rest of his day with a giant orange gourd on his head, he talking-pumpkins his regrets. "But the pumpkin should rot off my head in a month or two, right?"
Jim and Pam show up at work with Pam wearing a ball gown, tiara, stethoscope, and lab coat, explaining to Erin (in a puppy costume) that she's Dr. Cinderella. Jim explains how Cece's into princesses so they're trying to make them into role models. Erin likes that, but she's pretty crushed when Pam mistakes her for a dog instead of a puppy. Erin busts Jim on not being in costume, and Jim gets no support when he claims to be one of the Men in Black guys. Must be the blue suit.
The Halperts do a joint TH where Pam explains how Jim's normal clothes are related to "this sports marketing business that Jim told everyone about except for me," namely a big investment meeting today, which is why Jim forewent his usual minimal-effort costume. "Unless he has a secret costume that he told everyone about except for me." Jim remarks on the mileage Pam's getting from this. "Yeah, well, get used to it, bud," she smirks.
Andy walks into the bullpen dressed like Faith-era George Michael , complete with guitar, sunglasses, stubble, blond streaks, and leather jacket, although the back of his looks more like someone's couch. He reminds everyone to get their work done before the Halloween party after lunch, "or just throw it out." Angela, dressed as Nancy Reagan, announces that her husband the senator will join them later. Andy asks, "That reminds me, has anyone seen treble?" That cues the entrance by the Cornell a cappella group Here Comes Treble, coming in dressed like the Warblers and singing "Karma Chameleon." "What lab did these little clones escape from?" Dwight asks from behind his elastic-band pig-snout. "My Cornell a cappella group!" Andy says happily. Pam: "You were in an a cappella group?" Darryl: "You went to Cornell?" Andy laughs it off, slowly, and announces the group will be performing at the Halloween party. Stanley grumbles, but Clark acts enthused. "I love the boss's interests," he says. Meredith, dressed as some version of Catwoman, hits on them en masse. And in his office, Andy THs, as though it's just occurred to him, that he might be asked to sing "Faith," one of his signature songs. "I'm so not prepared," he lies.