This document discusses how design fiction and speculative design can be used to explore possible futures through fictional prototypes and worlds. It provides examples of early speculative design works from Bel Geddes, Superstudio, and Archigram. Design fiction is defined as using diegetic prototypes to suspend disbelief about change and explore potential objects and services rather than entire fictional worlds. Examples are given of how games can also act as a form of speculative design and critical design to allow consideration of alternate presents and futures. The document argues that speculative design works should enable a plurality of futures, be plausible, allow for both showing and telling stories, be iterative processes, avoid reductionism, and remain in a perpetual beta state.