Want to have the best dog costume ever? Check out this tutorial. ;)

Materials:

DOG TREATS (this is the most important material!)

cling/plastic wrap*
duct tape*
cotton filling*
stretch fabric (for bodysuit)
zipper
velcro
dog harness (base for wings)
upholstery foam
craft foam
1” or smaller PVC
sand
wire
hot glue
E6000 glue
large googly eyes
faux leather or
embossed scale fabric of your choice
3D fabric paint
metallic paint for eyes
cooling vest/ice packs
heat gun (or hair dryer)
scissors

*for optional step

This instructable was made with ZERO sewing. Some gluing steps can be substituted for a needle and thread.

Step 1: Optional Step: Duct Tape Mannequin

Completing this step will make the rest much easier! It will also save your dog constant fit tests and sizing. Some dogs will not tolerate this step. That is okay. Do NOT force your animal to do anything they are not comfortable with.

This step can be hot. Do this in a nice air-conditioned area.

Materials:

cling/plastic wrap
duct tape
cotton filling
(safety) scissors
dog treats

Ask your dog to stand. If your animal has been taught how to show stack, this is easier.
Cover your dog's fur in plastic wrap. Make sure all the fur around the body, legs, and neck is covered. DO NOT wrap your dog's head. Make sure the wrap is not too tight or too loose. Loose is better than tight. We are only making a form of the body.
Offer your pup some treats for being good.
Cut off strips of duct tape and cover the plastic wrap. Small strips of duct tape are easier to use than trying to use duct tape off the roll. Make sure you do not wrap the tape too tight. Work around the tail. Make sure the duct tape overlaps itself.
Offer more treats! Try to work quickly, but make sure you're careful. If your dog starts fidgeting or seems scared or stressed, stop. Use safety scissors to cut the plastic wrap and duct tape to free them. You can do this part in steps. A body form and legs. These can be attached separately if your dog is not comfortable doing the entire form in one step.
Once the plastic wrap is covered in duct tape cut the plastic wrap and duct tape. This is why LOOSE is BETTER! The best way to cut the form off them is one cut down the spine. BE CAREFUL. Use safety scissors and use a finger to make sure the scissors are not too close to their skin and fur. Usually once the spine is cut you can pull the entire piece off their body and down their legs. Make a cut down each leg if it is too tight. Always use your finger to keep the scissors away from your pet. It is better to clip your own finger than your dog!
Give your dog tons of treats and love once freed.
Seam up the duct tape skin with more tape.
Stuff the form with cotton and tape up the holes.
You're done! Go play with your dog.

Step 2: Body Form and Tail

Use that duct tape mannequin you just made! If your dog did not work with you and you do not have a mannequin, take your dog's measurements.

Materials:

stretch fabric
zipper
dog harness
upholstery foam
hot glue
E6000
scissors

Make the bodysuit. I used E6000 to glue the fabric. If you have a sewing machine, feel free to use it. Don't forget to leave or cut an opening for their tail! Leave the feet open.
Attach the zipper. I used a zipper along the length of his spine. I put his back feet in first, then his front legs, and pull the suit up and zip it up his back. Think about what is easier for you and your pet.
Put the dog harness over the bodysuit. Make sure it is adjusted to the size you want it. The harness should be well fitting to keep the wings in place.
Cut and glue your upholstery foam to create the shapes you want. It doesn't have to be perfect. It will be covered in fabric later.
I used craft foam for the tail because I ran out of upholstery foam.
Add extra foam at the shoulder blades.It will serve as the base and "muscle" for the wings.

Step 3: Wings and Flight Details

Depending on your dog, you may wish to size down the wings and skip the PVC. Do NOT use the PVC method for a dog that is not used to weight across their back/shoulders. PVC is still light, but can be dangerous for small animals or those not used to it. (My dog often hikes carrying a vest and pack. His muscles are developed to tolerate a bit of weight.) Make the wings small and with wire if your animal is not familiar with it.

Keep in mind that folded wings are much easier to make than large extended wings. It will allow your dog to maneuver more freely as well.

Materials:

PVC
sand
wire
upholstery foam
faux leather or embossed scale fabric
hot glue
scissors
heat gun (or hair dryer)

Cut your PVC (or have it cut at the store). Seal one end of your PVC with tape, fabric or glue.
Fill your PVC with sand. Tap the sealed end on the ground to pack the sand well. The sand will keep your PVC from kinking up when bent to form.
Heat your PVC with a heat gun or hair dryer and bend the PVC into the shapes you want. Hold it until it cools and heat another area to bend. Be careful of the heat and don't burn yourself. Use gloves if you need to. Once fully cooled empty out the sand.
Use upholstery foam at the base for muscles. Wings are meant for flight, and dragons are large beings! They need muscle to help them fly!
For the wings and tail, hot glue wire between the fabric for veining. Cover the PVC in the fabric.
A pet peeve (lol, pun not intended) of mine are dragon wings that do not have skin connecting to the body. An example can be seen where the Deadly Nadder's wings become smaller at the base. A wing needs surface area for such a large animal to fly! Use the fabric to connect to the body all the way down the back. This will help secure the wings.
Make sure your dog is protected from any points of the PVC by foam.
The base of the wings should be attached to the dog harness.

By folding my wings over the back, it gives another point for distributing the weight. It keeps them from breaking and is easier on the dog. If you do try the large wings, make sure they are balanced!

Step 4: Mask and Dragon Skin

I apologize for not having any templates in this instructable! This entire costume was made on the fly (d*mmit, another pun). If something didn't work, it was trimmed or tossed out and started over.

The mask (the entire costume) should not be worn for extended periods. Put it on for a photo or two and take it off. Not many dogs will tolerate it for longer anyway. ;)

Materials:

upholstery foam
hot glue
velcro
faux leather or ebmossed scale fabric
wire

Measure the length of your dogs head and make the mask 3-4 inches longer. Give your dog space to breathe.
For the ear/horns (whatever they are), push a piece of wire through the foam to help it keep its form and allow you to pose it if wished.
Use hot glue to piece it together. Hot glue melts foam, so be sure to hold it in place long enough to dry/cool. Don't burn yourself!
Test and size it often! You want it to be comfortable. (My dog uses it as a pillow sometimes. Lol)
Use velcro to wrap behind your dog's head/ears.

Give your dragon skin! These steps can be used on the body as well!

Hot glue your fabric flat to your foam around the edges. Again, the hot glue melts foam and will change the shape of your final product. The line in the center of the head (as seen in photo) was created with hot glue and holding the indent until cooled. The same process was used for the "eyebrows".
Be creative with your seams. I used a seam to create the mouth and nose!
On the body form, you can create pockets between the bodysuit and final skin for ice packs and cooling vests. Never ask your dog to wear his costume in the heat.

Step 5: Final Details

Hint: Make Alpha Toothless by making his spines out of resin with LED's in the base. Hot glue can be used in place of resin. ;)

Materials:

craft foam
3D fabric paint
metallic paints
large googly eyes
hot glue

Eyes

Pull the backing off the googly eyes and throw away the pupil. You only need the curved plastic. Be careful, the less expensive googly eyes have thin plastic that is easily damaged. You can use other plastics. I used googly eyes because they were available and the contour I needed.
Paint your eyes on the inside curve. Use metallic paints for the best effect. Leave the pupil clear! The mask is dark on the inside and leaving the pupil clear will allow your dog to see.
Glue the eyes into your mask. Leave some edges open to give the mask some airflow.

Scales

This one is easy and fun! Paint your scales onto your fabric with 3D fabric paint. Metallic is best.

Spines and Claws

Cut, fold and glue your craft foam into the shapes you need.
Start with small spines on the head and make them larger as you go down the back. Make them small again as you finish down the tail.
The smallest spines can be made with 3D paint!
Seal the foam with multiple layers of 3D paint.

Step 6: And You're Done!

Try the costume on and give your dog a ton of treats! Take them out for a photoshoot or halloween.

Never ask your dog to wear the costume for an extended period. Especially the mask.

Know the signs of stress and heat exhaustion! Some dogs are not cut out for costuming. Some just don't like it. Don't ask your dog to do something it is not comfortable with. If your dog becomes stressed or hot, take it off immediately.

Be vigilant. A dog's body language can be hidden in costume. Other dog's may be confused. Your dog's physical and mental health should be your number one priority.

Have fun. Play with your dog. Treat them well. They may only be part of your life, but to them, you are their whole world.

More costumes and images can be found on Facebook. Loki: Dog of Mischief