Young Indy

From the Lego Indiana Jones Wiki

Young Indy is a secret level that can be unlocked by doing all of the stages in Indiana's Office (located on the right side of the hallway in the middle door) then get the key, insert it in the key hole at the Artifact Room (after putting the diamond in). Then, turn the key (make sure you get all of the Artifacts from The Raiders of the Lost Ark). Then, enter the hole to your left and the title Young Indy will appear. After completing the level you will have Young Indiana Jones and Boy Scout. You will also be able to buy Fedora in the library.