Rainbow Unicorn is first seen when Joy, Sadness and Bing Bong sneak into Dream Productions so they could get an opportunity to see her in person; however, Joy is too captivated by the unicorn to even properly introduce herself. Later on, when Joy and Sadness attempt to wake up a sleeping Riley by infiltrating one of her dreams, Rainbow Unicorn accidentally appears on camera as she tries to sneak off with a plateful of cupcakes and other snacks. Some time later, she is seen onstage performing a dance number; however, the audience doesn't seem to be impressed at all. Her performance is then violently interrupted when Jangles bursts into the soundstage and causes mayhem.
Several of the boxes next to Rainbow Unicorn are marked "wigs", which may suggest her impressive hairdo is not as natural as it seems.