A police officer calls for backup at the "corner of Gardner and Fox", a reference to Gardner Fox, co-creator of the original Golden Age Flash.
Early in the story, Barry receives a post-card from Iris West, his former girlfriend, stating that she was now living in Paris as a successful artist. This was put in to explain why Iris, played by Paula Marshall in the Pilot, would not be appearing in the rest of the series.
When this episode first aired on network television, some close-up scenes of the mutated dog creature were edited out and viewers only saw the creature's shadow and some brief glimpses. When the series was aired in syndication and later released to home video / DVD, all scenes had been restored.