The cast also featured Cindy's parents – Bill (Clint Ritchie), a rancher, and Anne (Melissa Converse), a veterinarian.
[1] Thunder was always there to rescue Cindy and/or Willie in times of trouble "caused by others' misdeeds and thoughtlessness," including a forest fire caused by a practical joker, and Willie being hit by a stray bullet fired by teens in a no-shooting area.
Also playing a part in the adventures was Willie’s stubborn mule, Cupcake, who was trained to "burp" on camera.
Thunder was part of a 90-minute block of three live action shows to debut on NBC during the 1977 season, along with Search and Rescue: the Alpha Team and The Red Hand Gang.
Concerning international broadcasting, it is best known that in Italy the show ran in syndication in the early 80's under the title Fulmine (Italian for lightning).