We present an approach to decompose cartoon animation videos into a set of "sprites" --- the basic units of digital cartoons that depict the contents and transforms of each animated object. The sprites in real-world cartoons are unique: artists may draw arbitrary sprite animations for expressiveness, where the animated content is often complicated, irregular, and challenging; alternatively, artists may also reduce their workload by tweening and adjusting sprites, or even reuse static sprites, in which case the transformations are relatively regular and simple. Based on these observations, we propose a sprite decomposition framework using Pixel Multilayer Perceptrons (Pixel MLPs) where the estimation of each sprite is conditioned on and guided by all other sprites. In this way, once those relatively regular and simple sprites are resolved, the decomposition of the remaining "challenging" sprites can simplified and eased with the guidance of other sprites. We call this method "sprite-from-sprite" cartoon decomposition. We study ablative architectures of our framework, and the user study demonstrates that our results are the most preferred ones in 19/20 cases.