Long-term student retention and understanding of information is the goal of virtually all teachers/instructors/professors. One exercise was evaluated for its effectiveness to improve student retention of the nitrogen (N) cycle. This was conducted within a 3-h course entitled Soil–Plant Relationships that had a mix of M.S. and Ph.D. students. The N cycle was thoroughly discussed in class and students had prior knowledge that this information could be requested on unannounced quizzes. One week after this was discussed, an unannounced quiz was given and students were asked to provide a complete graphic N cycle. Prior to handing out the quiz, they were informed that proper completion of this material would qualify them as a Nitrogen Cycle Ninja (def: 1: individual with constant awareness and understanding of N dynamics, 2: warrior, perpetually ready for battle, and pursuing truth of all concepts as they relate to N in soil–plant systems) and they would receive a card that authenticated that achievement. Also, once this information was adequately learned, they could use their card (which had a miniature N cycle and list of all components) on all subsequent exams. Non Ninja card holders would not benefit from this privilege. Ninja status could only be achieved on unannounced quizzes, a sign of constant awareness and understanding of N dynamics. On the first quiz, only two students received their Ninja card. By the second pop quiz on the N cycle (given 14 d later), 16 of 17 students were certified Nitrogen Cycle Ninjas. An anonymous postclass student survey found that most students were pleased with the exercise. Three months after the final exam, 11 students were given impromptu visits and asked to provide the complete graphic N cycle, in addition to all components discussed in class. Six of the 11 students that were retested would have retained their Ninja cards. Students commented that similar approaches could be used for other subject materials. Also, most students noted that the exercise was fun, which increased their motivation to learn.