Yes, mule-mustangs! These kids were all wild-born mules. They are from the Twin Peaks HMA, which is the biggest HMA in California:
Today the herd is descended from US Army Cavalry remounts released prior to and during World War I, and historic draft and riding ranching stock. The horses are mostly bay, black, and chestnut, but pintos and appaloosas are somewhat common. Some horses even have a metallic sheen to them. The burros likely originated from historic sheep grazing operations in the area. Because Twin Peaks HMA has both horses and burros, it also is one of the few HMAs that has mules. The Twin Peaks animals are highly desired by adopters because of their size, quiet temperaments, and color.