This paper describes the design and fabrication of novel “soft” structures and mechanisms employing “smart” shapechanging materials. These structures and mechanisms incorporate shape memory alloy (SMA) micro-actuators, enabling them to exhibit lifelike movement when stimulated by the application of electric current. Fabricated by 3D printing in a soft elastomer material, their design includes internal channels into which the SMA actuators are easily mounted. Other design features allow flexibility of movement and facilitate cooling of the SMA actuators.A tentacle-like active structure is described, which incorporates an antagonistic pair of SMA micro-actuators, allowing it to exhibit two-way motion. Results are presented for the speed and range of motion of the tentacle-like structure.The paper goes on to describe a creative arts application for smart active structures and mechanisms which exploits the technologies under investigation: an interactive puppet which exhibits lifelike, expressive movement. This research in digital fabrication and smart materials has implications for the fields of interactive and robotic art and design, soft robotics and physical computing.