To dream of something being made of plastic represents your view of a person or situation being unimportant. Something makes you feel that it doesn’t matter. Your perception of something being powerless or not a priority.
Positively, plastic may reflect your feeling that someone or something is non-threatening or insignificant. Nothing to be worried about.
Example: A man dreamed of seeing a plastic person. In waking life he realized that a threat to his business wasn’t really a threat after all. He could finally move on with his business without worrying about anything.