Monster Mash is a sketch-based 3D model animation tool that allows quick character sketches, inflating them into 3D models and animating them. It requires a recent web browser with WebAssembly and WebGL support and can be controlled via mouse, touch, or stylus. It offers three creation modes: draw, inflate, and animate. The tool also allows for the creation/opening/saving/exporting of projects, with options for importing template and background images and exporting textured models in various formats. Hotkeys and settings such as armpit stitching and normal smoothing are also available.