Gwizdo is changed from how he was in the series. In the TV show, he is charismatic and fairly attractive. In the film, he's grimy and unpleasant.
Gwizdo's eyes are brown in the movie. In the series, his eyes are blue. Furthermore, in the movie, while Gwizdo needs his goggles to read, in the series his sight is perfect.
In one scene Gwizdo asks what the tree illustrated on the calendar is for, and Lord Arnold answers that it's for scale to compare to the size of the World Gobbler. This is a call-forward to the episode "Gland of the Mimikar", where Gwizdo finds a picture of a tree in an illustration of the Mimikar for scale.
The film is a prequel to the TV series, taking place roughly ten years before the first episode.
The film was released between the first and second seasons of the series.