Pronto is Spurs Jackson's horse. Spurs rides Pronto around his Bar-Z ranch in Arizona. When the Martian Korok takes Spurs and his ranch hands, Strong Bow and Hank Roper, back to Mars, Korok also orders Pronto to be brought along to the Red Planet. Korok intends on using the men and Pronto in his bid to depose Queen Thula by proving he successfully invaded Earth and become King Korok. The plan works for a very brief period before Korok is deposed.