Rumble is a light bluish-gray Pegasus pony with a dark-grayish sapphire mane. He is the younger brother of Thunderlane and seeks to follow in his hoofsteps to become a flyer for the Wonderbolts. When he comes under the impression that potentially obtaining his cutie mark in another skill or talent would prevent him from achieving his goal, he enters a phase in which he actively avoids getting his cutie mark. His fears are alleviated when Thunderlane, during a visit to the Cutie Mark Crusaders' recreational camp, shows Rumble his love of cooking in spite of his primary talent in flying.
In his one-line debut in "Hurricane Fluttershy", he is voiced by Ashleigh Ball. In his subsequent supporting appearance in "Marks and Recreation", he is voiced by Vincent Tong.