Animation layers and curves are essential tools for post-processing character animation, as they allow you to adjust, tweak, and blend different aspects of your animation without affecting the original keyframes. Animation layers are like layers in Photoshop, where you can add, subtract, or mix different motions on top of each other. Animation curves are graphical representations of the values and timing of your keyframes, where you can edit the speed, ease, and interpolation of your animation. Both Maya and Blender have built-in tools for animation layers and curves, but you can also use plugins to enhance their functionality and usability. For example, AnimBot is a paid plugin for Maya that adds a lot of features and shortcuts for animation layers and curves, such as smart keys, ghosting, snapping, and mirroring. For Blender, you can use Animation Nodes, a free addon that lets you create complex animation effects with node-based logic, or AnimAide, a free addon that adds more options and controls for animation curves.