Shadowfax is the lord of horses in J R R Tolkien's The Lord of the Rings, ridden by Gandalf and famed for speed and understanding. In Peter Jackson's film adaptation, Gandalf's whistle on the plains of Rohan in The Two Towers from 2002 summons the white horse from far off-screen, creating one of the trilogy's quieter iconic moments. The clip spread on soundboards as a shorthand for calling someone loyal and reliable, and it remains popular for edits where a character or pet answers a call instantly and without question.