The double horse does not exist. The double horse has never existed and never will. Stop asking.
Many people over the years have speculated about what a double horse would look like if one did exist, but this is a frivolous waste of time, because double horses do not exist.
The consensus among Centralian physicists is that the nonexistence of the double horse is a universal constant, unlike the speed of light, which can totally change if you want it badly enough.
PrincessMeredith once claimed to have a higher tolerance for dangerous drugs than a double horse--an utterly meaningless statement, because double horses do not exist.
TheUniversityOfCentralia's sports mascot is called the Double Horse. Nobody knows what the mascot looks like, because double horses do not exist.