Internal and external validity are key concepts in understanding the scientific method and fostering critical thinking. This article describes a class demonstration of a "botched" experiment to teach validity to undergraduates. Psychology students (N = 75) completed assessments at the beginning of the semester, prior to and immediately following the demonstration, and on an examination. Results indicated that students significantly increased quiz scores across 3 assessment points, scored higher on experimental validity questions on an exam, and increased use of critical thinking skills in a novel application. The demonstration engaged students during class and increased comprehension on the topic of experimental validity. (Contains 2 tables.)