Dr. Slump: Arale-chan - episode 16 - 28 Jul, 1981

Arale finds a camera which will show the future. She takes everyone's photo with the camera to see how the future will be 10 years later. All of her friends become 23 years old, but Arale is still the same.... Arale Norimaki and Akane Kimidori decide to change their appearance to look like each other and spend the rest of their day pretending to be the other. (Source: Wikipedia)