SpongeBob SquarePants and Patrick Star have somewhat similar looks. They have big eyes and simple body shapes. Also, their personalities complement each other, which adds to the similarity in their overall appeal.
I'm not really sure what you mean by 'old devi cartoon'. Maybe it's a specific type of old cartoon featuring a character named Devi, but I need more context to be certain.
First, get some paints or colored pencils. Decide on a theme for your egg, like a cute animal or a fantasy scene. Then start filling in the colors gradually, making sure to blend them smoothly for a great look.