An important note for those that say everything is doctored and/or composited.
For the image to look right, not only does the lighting and the position of the subject and the camera have to be the exact same, but also the film and lens need to be the same. And the tampering has to be seamless and undetectable. The odds of all of that happening successfully are very slim.
The only time any photo can be a real successful composite, is if they were taken in the same studio at the same time, and the subjects swapped places moments apart. And if that were the case, that means the Beatles would've had to have been coexisting with the 'Featles'.