Koko, a green and purple high-speed train, is one of the young engine trainees. She is styled after a bullet train. Adventurous and competititve, she enjoys exploring and challenging other trains to races. She is also somewhat mischievous, which can get her and her friends in trouble. Her catchphrases include "Chugga chugga choo choo!" and "Can't catch Koko!"
Koko is part of the land of Chuggington, where trains come to life! In this train-based world, the "chuggers" are talking characters based on trains of all types, from old steam engines to sleek new bullet trains. Based on a 3D CGI television series for preschoolers, the land of Chuggington is action packed and energetic. Each episode is entertaining, with lots of positive life lessons mixed in. Little fans will learn about values such as friendship, hard work, and sharing while they root for the three young "trainees" - Wilson, Koko and Brewster - as they learn to ride the rails in Chuggington.