Hidden Runner, voiced by Rob Paulsen, is a character whose only appearance, so far, has been in the TV series episode, "The Spooky Nighttime Adventure". He is, as his name implies, a Hidden Runner. He has the ability to blend in with his habitat due to his multi-colored markings, giving the impression that he can turn invisible.
Hidden Runner was thought to eat meat, hence why he was feared. However, as he doesn't appear to be a Sharptooth, and because the characters find his bite marks on some plants while searching for him, it seems more likely that he is an herbivore or omnivore.
- Hidden Runner is believed by some to be a Sinornithomimus, while others consider him to be a Troodon or an Ornithomimus.
- While in the cave, the Hidden Runner's silhouette shows him with teeth and a Sharptooth-like appearance, very dissimilar to how he actually looks when the characters find him.
- Unlike most of the dinosaurs in The Land Before Time, which sport relatively simple color pallets, the Hidden Runner is one of the most vibrantly colored characters in the franchise. Other dinosaurs and creatures designed with vibrant colored markings are the Archaeopteryx, Opthalmosaurus, and the Rainbow Faces.