OuroWorld is a mask-free framework that turns any static 3D Gaussian Splatting scene into a 3D cinemagraph — a dynamic scene with vivid, diverse motion looping seamlessly from any viewpoint. A vision-language model infers plausible dynamics and guides a video model to synthesize a reference video, which is then lifted and completed into multi-view videos. To learn from this imperfect supervision, the authors propose Inconsistency-Robust Periodic 4DGS: a Fourier-series deformation field that guarantees looping by construction, plus a Grounded Drift Field anchored at the reference view to absorb cross-view inconsistency. On 39 reconstructed and generated scenes, OuroWorld outperforms all baselines and wins 70.8%–99.0% of user-study comparisons.