This article describes a classroom activity to demonstrate (dis)agreement in personality judgments, using an exercise derived from Watson's research on the accuracy of rating strangers' personalities. On the first day of class, undergraduate students in psychology courses rated their own personality and the personality of a classmate, using items from the International Personality Item Pool (IPIP). Across five samples, self-other correlations were strong for extraversion but varied for the other four traits. Comparisons with control groups on relevant test items provided preliminary evidence that the exercise promotes learning of relevant material. This exercise can be used in introductory or personality psychology courses to facilitate discussion of various topics including interpersonal judgment and accuracy and methodological and statistical issues. (Contains 2 tables and 2 notes.)