Motion blur is a well-established technique which prevents strobing by making fast moving objects appear blurred. In cel animation however, different methods are used and we present a new technique to emphasise the motion of cartoon objects through the application of geometry. We term the involved nonphotorealistic motion blur as 'cartoon blur'. In order to express cartoon blur, we have classified the expressions used in cel animation and analysed the diversity of each expression to establish parameters that allow animators to control the expression.