Ducky is the green 'Saurolophus', also known as "Big Mouth" or "Swimmer" from the Land Before Time franchise. She comes across as one of the more naive of the characters. She very rarely uses contractions in her speech but often ends her statements with her trademark, "Yup, yup, yup."
Ducky was voiced by Judith Barsi in the original Land Before Time movie. Heather Hogan voiced her in the next three films before Aria Noelle Curzon took over the role for movies 5-13 (so far) as well as the television series.