You can never really be too young or too old to dress up, right? And who doesn't want their own little demon baby?
Since Halloween is coming up, and I just became a mom just two months ago, and thus I'm clearly not going to any Halloween parties myself, I might as well dress up the baby instead.
I also just got hold of this mouldable plastic which is amazing for this project!

For this project you will need:

A baby-favourite type of pacifier (it sucks spending too much time only to find out baby hate that type of pacifier)
Mouldable plastic
Black acrylic paint

Tools:

Moulding tools
Paintbrush
Boiling water (put some on a thermos to have it handy)
Lighter/candle
Scissor

Step 1: Making a Base

First you need to cut off the ring of the pacifier, as we won't be needing it. You might however be careful not to cover both (or either) holes where the ring was attached as this allows air to get in, and escape, making it more comfortable when the baby is sucking/biting on it. If you happen to cover it a bit while the plastic is still soft, just keep pressing the silicone part to blow air through, and it will likely form a little hole by itself.

Follow the instructions of your plastic, and add your plastic pebbles to boiling hot water. No need to add any pigment yet. I can't say for sure how much you need as I always eyeball that sort of thing (if you make too much, it can always be recycled and melted again).
Shape the mouth. Confuse baby by exchanging regular pacifier with new mouth pacifier. Make sure the mouth is curved right.

While the plastic is still soft and mouldable, adjust the curve to match the baby (careful not to burn the baby! The plastic can be pretty hot when its fresh from the water, so wait a little).

Step 2: Adding the Inside of the Mouth

I had some leftover red and added one blue pebble to get this great dark flesh like colour for the inside of the mouth. You don't need an awful lot.

Press it flat and stretch it as thin as you can. Use a scissor to cut it to match the shape of the mouth. Using the heat of a candle, heat up the outside of the mouth and add the red on top. Remember to press the silicone sucker to create an air hole.
If you get a few spots of white where the red didn't reach, you can cut up fitting pieces of red and patch those places. Gently heat up the areas to even it out with your fingers.
Using some kind of moulding tool, create ridges for lips.

Confuse baby one more time, and adjust the shape one last time.

Step 3: Teeth! Lots of Teeth!

(These would've been really awesome with glow in the dark pigment, but unfortunately I didn't get that pack)

The teeth need to be slightly yellow to have somewhat of a natural look, but the yellow pigment I got for my plastic is somewhat strong, so I had to cut a pebble in half (soften it a bit in the boiling water first).

Make two teeth at a time before adding anything to make sure they have the same size. I like to make mine narrow and sharp, so I used a scissor to sharpen some of the teeth. To give the fangs a bit of depth, and not just look like two pieces of flat plastic, I added a little sausage in the widest end, and evened it out.

Start in the middle! Find the middle of the mouth (you can draw a line from where the silicone sucker is attached on the other side) and make superficial markings with your nail. Heat up the teeth and the mouth and stick the first two middle teeth on, and work your way out. Always start in the middle with the teeth closest to the centre of the mouth to make sure you place them right according to each other.

Each time you've added a tooth, dip the mouth in ice water to make it harden. It makes the plastic stronger, but it also cures the plastic faster so you can continue working on the other side, sticking the next tooth on, without accidentally ruining anything else thats still soft.

Step 4: Add Shades

I had a bit of left over red to emboss the lips a bit more, and give a better impression that the teeth are underneath the lips, not on top of them. Give the teeth a light heat with a flame and smooth away any finger prints. Heat it a bit again and finally drop it in ice water for a few minutes.

With a bit of watered down black acrylic paint, paint some shadows between the teeth, while at the same time using a clean brush and water to clean off the teeth (and wipe with your fingers).. Gradually use less water and darken closest to the roots of the teeth, constantly cleaning off the teeth.