We introduce a design strategy, alien presence, which combines work in human---computer interaction, artificial intelligence, and media art to create enchanting experiences involving reflection over and contemplation of daily activities. An alien presence actively interprets and characterizes daily activity and reflects it back via generative, ambient displays that avoid simple one-to-one mappings between sensed data and output. We describe the alien presence design strategy for achieving enchantment, and report on Tableau Machine, a concrete example of an alien presence design for domestic spaces. We report on an encouraging formative evaluation indicating that Tableau Machine does indeed support reflection and actively engages users in the co-construction of meaning around the display.