Pillow is an interactive pattern-design system for creating plush toys. The user imports a 3D surface model into the system and specifies the segmentation boundaries interactively by drawing seam lines on the model surface. Based on this segmentation, the system generates a 2D pattern by flattening each outlined region, and then visualizes the shape of the resulting plush toy by applying a simple physics simulation. If the result is not satisfactory, the user can make different seam lines. This closed-loop framework allows users to experiment with various seam patterns before actually working on real fabric to obtain the best-looking result. The system also estimates total sewing time based on the total length of the seam lines. We implemented the system to produce plush toys and a balloon.