Complex sentence: An early example of the teaser trailer was the one for the "Superman" film by Richard Donner when as the film was already nearly a year late was designed to re-invigorate interest in the release.
Split into simpler sentences: An early example of the teaser trailer was the one for the "Superman" film by Richard Donner. The film was already nearly a year late; it was designed to re-invigorate interest in the release.