My Platypus uses the same hex base as my Lizard, Turtle, and Armadillo. The main challenge here was to get a good looking head (and as always the shoulders). The model includes a color change for the bill, although you can't see it here because the model shown is folded from single-color paper.

Cats and dogs are challenging subjects because they're so familiar to humans. This model was inspired by the animal adoption service Timber's Legacy. Having the subject in a sitting posture allowed me to focus more on the overall shape and sculptural aspects rather than worrying much about the base and where the points for all the legs would come from. This dog has pointy ears, which is rare in origami dogs.

Once I had my dog worked out, I figured the cat would be a simple variation, but it turned out the pretty different. Not only is the head and face totally different, but the long tail required a whole new geometry and base. Finally, the body posture, neck and shoulders were different enough to have to come up with a new treatment. It took quite a few iterations before I had the details refined enough to attempt one out of good paper.