In the wooded area of Fort Wasteland is a giant bull’s head. Use the cut trees to ascend to it, and cross the rotating horn to the nearby ledge to find the trapped Gremlin.
The next Gremlin is on ledge in the beach ball slope section of the Floatyard. Ascend the ledges until you reach the Goofy plates, and hop over to the ledge where the Gremlin is caged.
There are a few ways to find the Gremlin in Ventureland, but one method is by far the easiest. When you reach Pete Pan’s booth, simply turn left and head through the tunnel to find the Gremlin.
The next Gremlin is in Autotopia. In the southeastern section of the zone there are some trees you can thin out. Do so and us the car next to them to hop onto the hidden ledge where the Gremlin is trapped.
The final Gremlin is Jamface himself, who is trapped in the Mad Doctor’s Attic. He is freed during the story.
After freeing every Gremlin, speak to Jamface in Mean Street North to complete the quest.