"Design a playful, stylized 3D model of a cartoon backpack. Use rounded, exaggerated shapes and bright, bold colors to create a fun, approachable look. Add oversized zippers, chunky straps, and whimsical details like badges, patches, or keychains to enhance personality. Keep textures simple and clean — flat, cel‑shaded, or painterly — to maintain the cartoon aesthetic. The overall design should feel lighthearted and appealing, perfect for animation or children’s media.