I will present three very different works in human computer interaction that play with our perception in surprising ways. Ostensibly, they address problems in interaction, but there is also an element of fun and pleasure to be experienced, or at the very least surprise. While in our field three exemplars is enough to lay claim to an unassailable generality, the three projects I will talk about are so radically different that a coherent theme would be a real stretch. Yet together they suggest how recent developments in sensing and display technologies allow us to manipulate the user’s perception in new and evocative ways.