Rainbow Unicorn is a character in Inside Out. She lives in Riley's mind at Dream Productions, where she stars in Riley's dreams. She was notably in a dream titled Fairy Dream Adventure Part 7. Joy is apparently a huge fan of her.
When Joy and Sadness along with Bing Bong sneak into Dream Productions, they get the chance to see Rainbow Unicorn, though Joy proves to be too impressed to introduce herself properly. Later, as Joy and Sadness try to wake up Riley by infiltrating a dream, Rainbow Unicorn accidentally appears on camera as she was sneaking away with a full plate of cookies. Later again, she appears onstage performing a dance, which doesn't seem to impress the audience at all. Her performance is then brutally interrupted when Jangles the clown bursts into the soundstage.