Former watermarking techniques have been largely developed for application to natural videos. Important applications, including virtual reality, computer games, cartoons, and movies, involve another category of visual data: computer animation. In this study, we developed robust watermarking techniques to protect MPEG-4 2D mesh animation against copyright infringement. Three time-series analysis tools, the discrete cosine transform (DCT), singular spectrum analysis (SSA), and discrete wavelet transform (DWT), are employed to analyze the motion characteristics of mesh animation. The watermark is cast upon the important motion components by employing the spread-spectrum principle. During watermark extraction, a spatial-domain least-squares registration technique is used to restore the distorted mesh. Each watermark bit is then detected by a hard decision with the aid of cryptographically secure keys. We have tested the proposed system against a variety of attacks, including affine transformations, temporal smoothing, spectral enhancement and attenuation, and additive random noise. The time-series analysis tools studied here are evaluated in terms of their robustness to attacks and the required computational complexity.