Here’s a tutorial I did a few years back for deviantART. I needed to create an ad for a local rec program, featuring a picture of a young man happily working with a kid. The problem was, while I had the perfect stock photo for the job, the young man had a very serious look on his face. It didn’t look like he was having much fun, which really wasn’t the best look for the ad.
The solution? Perform face transplant surgery, Photoshop style!
Step 1: Find a Donor
First, find a photo with a face that has the expression you’re looking for. The head should be at roughly the same angle, although side-to-side tilt can vary. Also, be aware of skin differences, like freckles, etc.
Step 2: Begin the Graft
Select the feature you want to replace. In this case, we’re interested in the mouth. Copy and paste or drag it to the original face. I named this new layer “New Face” (creative, I know!)
Step 3: Begin the Reconstructive Surgery
Press Command + T (Windows: Ctrl + T) to rotate and resize the new mouth to line up with the angle of the original face. Don’t worry if the cheeks, chin and neck don’t line up exactly, as long as the main features are in the right place, and are roughly the right size.
Step 4: Adjustments
With the New Face layer selected, press Command + L (Windows: Ctrl + L) to adjust your levels. You may have to make other color adjustments to fit your images. My final image was going to be in black & white, so I wasn’t worried about matching the color perfectly.
Step 5: Blend it in
With the new face layer selected, press the Add Layer Mask button 
on the layers palette. Select the layer mask (the white box will have a black and white border). Click the brush tool in your tools palette, and in the brush options, choose a medium size diameter and 0% hardness. The areas of the mask that you paint black will disappear, but will not be erased. If you make a mistake, simply switch to white, and brush over the area you want to reappear.
Don’t forget: All the muscles of the face are interconnected. Since I was changing the face from serious to smiling, I had to replace the original eyes to keep the smile from looking fake. The process for the eyes, which I took from the same donor face, was exactly the same as before.
The Finished Product
I converted the image to grayscale, because it was going to be printed in a black and white newsletter. And here’s our finished product.
One Final Note
This is a LOT easier to do with a graphics tablet. I currently use a Wacom Graphire Bluetooth 6 x 8-Inch Tablet
