During your first visit to Ostown, you helped clean up the Thinner pool mess (either by using Gremlin Jamface's idea or Gremlin Prescott's). On your second visit, Goofy will offer you the quest. Some pieces of the Oswald statue has fallen in the sinkhole and recover them. Explore the sinkhole and recover the statue pieces by moving them to the Transport Tubes. Deep inside, there are two paths: one leads to a Mickey head and another path leads to the original Oswald head.
Thinner (Mickey) Path
Bringing the Mickey head to use on the statue will win you the Heads, I Win Pin.
Paint (Oswald) Path
Using the Oswald head on the statue will give you the Good Head on His Shoulder Pin and in Episode 3, you can build a Mickey statue by talking to the Green Gremlin in the Gag Factory in exchange for Scrap Metal. This will complete the Heroes of Wasteland Challenge.
Also, if you fix the statue, this will stop the Thinner flow from spraying Mickey's House (Clarabelle and Ortensia's house too if you used the supercharged pump in your first visit), thus, you finally gain entry and can continue the Creative Threedom quest.