They go to Hollywood to look for a make-up artist, the man of 1000 faces. When they enter his laboratoy you can see boxes of eyes, teeth, noses and hair. When he steps outside his lab, Ringo decides to enter a strange machine.
Then the other three step inside (McCartney song) and all 4 come out as Ringo.
Another Frankenstein reference.
Bottom right is out of sequence. They did eventually switch back to their 'normal' selves.
There's also a mention of split-personalities in this one.
Youtube link: http://www.youtube.com/watch?v=FV1K_zBoJEg