Anyone playing around with Photoshop or similar programmes will know how to do this type of composition. For this reason I am not going into any great detail but I will show you how I did it seeing as you have visited out of curiosity. I just happen to find these fun things an easy way of relaxing from my daily job of restoring photographs.
Ok step 1 is to find some suitable pictures that will blend together. Take into account colours and light source as these are the most important.
Step 2 is to remove all the background from the crocodile using whichever method you prefer. There’s a hundred ways to do this but I mainly use the pen tool or the eraser tool. They are both pretty fast and will be as accurate as you need for the job in hand.
For step 3 all you need do is paste the crocodile head over the head of the frog and resize to taste. Some soft erasing will be required around the croc’s jaw and where the frogs eyes are. At this point you have a choice of removing the croc’s neck making a longer jaw, or fading in it’s neck as a kind of folded layer of skin (As I have done). Don’t forget to clone the croc’s eye out unless you want something really spooky.
Step 4 needs a little understanding of both animals body structures as this will help them compliment each other. The frog has some quite striking features that can be used for this and the photo here shows you how I used them to help blend them together. Step 5 requires a little knowledge of colour matching 2 subjects. Just make a colour balance adjustment layer and play with the levels until you find something that makes the composition more believable. Once this is done, mask out the inside of the croc’s mouth and its teeth and you are pretty near completing your match. Your crocofrog tutorial is almost at an end. Step 6 only needs some burning and dodging. Try following the shadows and highlights on each of the animals. Blend them into each other giving it that final touch of realism.
Your photo should now look a little like this or more probably better if you’ve taken your time about it.