Puff and the Incredible Mr. Nobody(1982)
Puff the Magic Dragon pays a visit to a little boy whose creativity has been stifled. Terry's only friend is an imaginary duck named Mr. Nobody, so when Nobody flees to the Fantaverse, Puff takes Terry to find him and teach the boy that Nobody is really somebody!
This is the third and final film based on the popular song by Peter, Paul and Mary. Burgess Meredith ("Batman," "Rocky," "Twilight Zone") voices Puff for the final time, and Billy (Jayne) Jacoby ("Just One of the Guys," "Parker Lewis Can't Lose") provided the voice of Terry.