The Lone Ranger and Tonto rode up to a saloon and went inside. A few minutes later a cowboy comes in and asks "who's silver horse is that?" The Lone Ranger replies that it is his, why do you ask?
The cowboy says he looks overheated you should cool him down. So The Lone Ranger tells Tonto to go run circles around Silver until he cools down.
A few minutes later another cowboy comes in and asks "who's Silver horse is that outside, to which again he replies that it is mine, why do you ask?
The cowboy says... you left your Injun running.