We propose a thermoformable shell called TF-Shell that allows repeatable thermoforming. Due to the low thermal conductivity of typical printing materials like polylactic acid (PLA), thermoforming 3D printed objects is largely limited. Through embedding TF-Shell, users can thermoform target parts in diverse ways. Moreover, the deformed structures can be restored by reheating. In this demo, we introduce the TF-Shell and demonstrate four thermoforming behaviors with the TF-Shell embedded figure. With our approach, we envision bringing the value of hands-on craft to digital fabrication.