The Other Unicorn is a female Unicorn.
A white-furred Unicorn with a golden horn and a pure white mane (as opposed to Unie's black one), this female lives in the Himalayan peaks near the Valley of Shangri-Lala. Her existence was discovered by a correspondent of Scrooge McDuck's in 2008, and he subsequently sent Donald Duck and Huey, Dewey and Louie Duck there with Unie the Unicorn, which he had, thus far, believed to be the only natural Unicorn still living.
He hoped that Unie and this Other Unicorn would breed and produce offspring, thereby saving the species and providing Scrooge with several more valuable animals for his zoo, in one fell swoop. The first part of the plan went quite well — as Unie and the Other Unicorn instantly hit it off, the mare being smitten with Unie's strength and short temper — but Donald and the triplets ended up refusing to bring the two Unicorns back to Duckburg, seeing them so happy in their natural habitat.
Behind the scenes
The Other Unicorn first appeared in the 2008 story Trail of the Unicorn.