Just Mickey (Fiddlin' Around , Fiddling Around) (1930) - Mickey Mouse Theatrical Cartoon Series

In this cartoon you can clearly see the discontinuous design of Mickey's face, especially the eyes and eye-lids. In the more closer shots (during the "sad" melody) he's got a double outline of the "mask", a relict of the huge eyes of the very first days plus small eyelids in the center, except for the big pupil this is the same principle as with today's Mickey. At the end of the short he got his old eyes back again.