Research: Howard S. Moss

"The earliest known use of replacement faces appears to be from the MoToy Comedies by American filmmaker Howard S. Moss in 1917." 
http://www.awn.com/animationworld/advanced-art-stop-motion-animation-building-puppets-part-4

As Howard S. Moss was one of the first people to experiment with face replacement animation, the facial animation in 'Mary & Gretel' (his first face replacement animation) is very simple. The faces are replaced to change the expressions on the characters faces for different shots but as far as I could see the faces were never changed mid shot, this leads me to believe that Moss struggled to replace the faces without moving the character. Because of this I will play around with the layout of the back of my faces as well as experiment with different ways to attach the faces. 

By 1930 Moss had greatly improved his face replacement skills as he was replacing the faces multiple times in each shot to show a range of emotions as well as speech (even though there was no dialogue).  In the animation below 'Dolly Daisy in Hearts and Flowers' we see a woman who has the choice of two guys; she picks the richer of the two until his car breaks, then leaves him for the other man before flying off holding a balloon. Throughout this animation face replacement is used to show the expressions and moods of the characters. Even though the facial animation could of been made smoother with a few more in betweens, the animation was really good for its time and should be an inspiration for anyone exploring face replacement animation.