Making tongue as a frog
Open the two photos of a frog and a girl, who stuck her tongue out.
Use the Select By Color Tool to pick the color of the white part of the image of the frog. Invert the selection and copy the frog. Paste it as a new layer on the image of the girl.
By using the Rotate Tool turn the frog at the desired angle (-50 degrees). Use Move Tool to place it on the tip of the girl’s tongue.
Use selection tools to trim unnecessary parts of the frog.
Now you must copy the tongue’s parts and place them under the frog on the new layer. In order to see whether tongue’s parts are placed correctly you should make the layer with the frog transparent, just to keep it visible (change opacity).
In the Layers tab activate the layer with the frog. Click the right mouse button and select «Alpha to Selection» in the pop-up menu. Then invert the selection and activate the layer with the copied tongue. Remove from the layer all regions under the selection.
Now you should clean this layer because it may contain excess points. Besides, you must make a smooth transition from the real tongue to the copied one. Set the blending mode «Overlay» to the layer with the translucent frog to make it more realistic.
Then merge the layers with the frog and the tongue. Click the right mouse button on the resulting layer and choose «Alpha to Selection». Create a new layer and use soft-edged brush to make the frog more three-dimensional. Pass the brush with a black color over the selection’s outlines. Then set the «Overlay» mode to the layer, which should give the volume.
Also you must create a shadow below the new tongue. Create a new layer between the original photo layer and the new tongue layer. Set «Overlay» blending mode to this layer and pass the same soft-edged black brush over the frog’s outlines.
Merge the layers. Our frog is almost ready. Now you must add volume by using not shadows but light. Use the paint tool «Clone» to clone highlights to the wanted areas of the new tongue. As well, you can create a new layer with the «Overlay» blending mode and using the soft-edged white brush add light to the desired regions.
I get the final full-scale result as follows: