Dorami & Doraemons: Robot School's Seven Mysteries(1996)

It is time for Doraemon's younger sister - Dorami-chan to graduate from the Robot School. But a mysterious wind sucks Doraemon and the principal away. Dorami escapes, and finds Doraemon's Good Friend Telepathy Card. This is a device Doraemon uses to communicate with his friends—collectively known as The Doraemons.