In this Season Three kickoff of Chatbots Behaving Badly, I finally turn the mic on one of my oldest toxic relationships: my “AI-powered” electric toothbrush. On paper, the Oral-B iO Series 10 promises 3D teeth tracking and real-time guidance that knows exactly which tooth you’re brushing. In reality, it insists my upper molars are living somewhere near my lower front teeth. We bring in biomedical engineer Dr. Erica Pahk to unpack what’s really happening inside that glossy handle: inertial sensors, lab-trained machine-learning models, and a whole lot of probabilistic guessing that falls apart in real bathrooms at 7 a.m. They explore why symmetry, human quirks, and real-time constraints make the map so unreliable, how a simple calibration mode could let the brush learn from each user, and why AI labels on consumer products are running ahead of what the hardware can actually do.