Nessie is a sweet and beautiful creature. She gets sad very easily when something awful happens to her. For example, MacFroogle taking over her home to make it a golf course.
Nessie once lived a peaceful live in a small pool with her rubber duck McQuack, until Tycoon MacFroogle paved it and the surrounding land over to create a golf course. Though so distressed that she wanted to cry, she was dissuaded from this course by an observing bird and so decided instead to find a new home. However, every attempt proved fruitless, and each observer she encountered expressed the same sentiment against crying as the bird. Finally, after a long journey without success, Nessie broke down and cried a literal flood of tears; once they were spent, she discovered to her astonishment that they had produced a perfect new home for her: Loch Ness where she and her rubber duck, MacQuack would live peacefully forever afterwards.
Nessie can be spotted in two scenes as a figurine in the holiday short Olaf's Frozen Adventure. She is first spotted during the musical number "That Time of Year" and later during the scene when the sled is on fire.