Deliberate mistake: There are two Ewoks Wicket's parent is in search of. One of the those Ewoks is seen climbing down a mountain and the other has finished climbing down. As this happens, look at the Ewok not climbing. As he bends down, you can see half way down his left leg, there is some sort of fold there. This is mainly due to the fact that the Ewok actors wore costumes whilst filming. The fold is coming from the Ewok costume.
Continuity mistake: The tree creature pulls Mace's right hand and arm into the tree. Later, after giving Cindel the medicine, an Ewok examines the wound, which has switched to his left hand.
Continuity mistake: The ferret present during the scene where Wicket and Cindel talk about star cruisers disappears between shots. This is most noticeable when Mace walks in and begins talking to Cindel.
Other mistake: When Mace and Cindel are running from the boar-wolf, sunlight is visible between the trees. It's supposed to be nighttime during this scene.