Iconodiagnosis, the reading of clinical signs in works of art, brings together dentistry, art history, and the medical humanities. This article examines The Laughing Fool (c. 1500), attributed to Jacob Cornelisz van Oostsanen, in which the laughing figure displays a pronounced gummy smile with visible gingival changes. Inspecting the painted mouth as one would a patient, we identify an excessive gingival display and signs of mild gingival inflammation, features consistent with the phenotype recognised today as a gummy smile. This early depiction illustrates how direct observation has long underpinned diagnosis, well before modern instruments, and suggests that such paintings hold value for teaching observation in dental education.