A lot has been made of the topical puzzle Su Doku, with various claims that it can support development of mathematical abilities. The latest, in March this year, came from the Training and Development Agency when a giant puzzle was used to attract graduates into a career of maths teaching. A giant Su Doku puzzle toured busy city centres with the aim, according to Michael Day from the agency, "to capture the attention of graduates and students and encourage them to consider the rewards of a career in maths teaching". In this article, the author wants to highlight the insight that exposure to Su Doku problems can offer when it comes to mathematical problem solving and the communication of understanding and thinking. He describes how two of his students' familiarity with Su Doku affected the way they discussed a three-dimensional problem solving task. (Contains 2 figures.)