Prompt: "A vibrant and eye-catching YouTube thumbnail for a children's ABCD song. The main focus is large, colorful, and playful 3D letters A, B, C, and D, each with friendly, smiling cartoon faces. The background is filled with a bright, cheerful rainbow gradient, decorated with fun elements like twinkling stars, colorful confetti, and musical notes floating around. Include happy, cartoon-style children joyfully singing and dancing around the letters, with one child holding a microphone and others clapping or jumping. Add cute, animated animals like a happy monkey and a giggling giraffe, engaging with the letters, creating a lively and energetic scene perfect for young viewers."