In the scene right after the escape from the Emperor's jail, you meed Howard who asks you for a can of oil. In order to give him some oil, you use the can that you bought from the pawn shop on the chute next to the robot guard and then exchange the oil can for the pure oil in the bar. However, you must inspect the tin can after loading it with oil from the chute in order to receive the lever! If you happen to exchange the tin filled with oil with the pure oil from Johnny B. Goose, then the lever may be lost and unrecoverable such that you will not be able to complete the scene at the doctor in order to get inside the robot suit.