During the cold and drizzly Pacific Northwest winters, it feels like I’m always a little chilly and can never quite warm up. In Scandinavian countries where the winter months are similarly cold, wet and dark they are very familiar with this situation. To combat the cold dark winters, the Danes have a concept called “hygge” - meaning cozy comfiness.

Inspired by this idea, I wanted to make something warm and furry for lounging about the house. It occurred to me that one can find furry slippers, fur gloves, fur hats and fur coats at stores. But where are the furry bottoms? No fuzzy shorts, fleecy underwear, caveman pants, nothing. Is not the middle part of our body as deserving of furry warmth as the rest? Urimelig - as they would say in Danish - furry bottoms had to be made.

In these couple of steps you will see how easy it is to use a pair of your undies as a pattern to create a pair of hygge hotpants that are furry on the outisde and lined with the undies themselves.

WARNING: Those that don these snuggie skivvies may find they need to wear little else!

Materials:

1 Pair of underwear for lining
⅓ to ½ yards of fake fur
Thread to match fake fur
Large sheet of paper to make pattern

Tools:

Pen for drawing pattern
Measuring tape
Exacto Knife or Scissors
Cutting mat (if you’re using an Exacto knife)
Sewing Machine
Hand needle for finishing stitches
Pins

Step 1: Create Your Pattern

For this instructable, I made two pairs of hygge hotpants -- one from a pair of lady's booty shorts and one pair of fella's boxer shorts.

(The instructions are basically the same, except that for the long boxer shorts we have to edit the pattern slightly to account for the crotch space needed.)

Booty Shorts

Fold your underwear in half so that the butt part of the underwear is on the outside.
Place the folded underwear on paper and trace around the edge of the shorts. 
Measure the width of the shorts, and add 25%-40% in width to account for the fabric stretch. (In the image you'll see three little arrows pointing left where I added about 25% width for stretch.)
Now add about 1cm around the whole edge to account for seam allowance.
Now fold the underwear the other way, so that the front part of the underwear is on the outside.
Trace around the edge of the shorts. You may have to push the fabric from the back out of the way to properly trace the front side. (Don't worry if it's not perfect -- this project is very forgiving of imperfections.)
Add 25%-40% width for stretch.
Add 1cm for seam allowance.
Cut out the two sides!

Long Shorts

Fold your underwear in half
Place the folded underwear on paper and trace around the edge of the shorts.
Measure the width of the shorts, and add 25%-40% in width to the straight side to account for the fabric stretch. (In the image you'll see four arrows pointing left where I added about 25% width for stretch.) 
On the side with the curve, you're going to invert the curve so that it goes the opposite direction. (See the drawing for reference)
Now add about 1cm around the whole edge to account for seam allowance.
Cut out this one side!

Step 2: Cut Out the Fabric

Get out your cutting mat and Exacto knife.

You're going to cut out four pieces of fabric per pair of shorts.

Booty Shorts:

Take one of the two patterns and set it on the fabric with the pattern face up. Cut out the piece of fabric.
FLIP THE PATTERN OVER and cut out another piece.
Now do the same thing with your second pattern, so you should end up with a total of four pieces.

Long Shorts:

Take your pattern and set it on the fabric with the pattern face up. Cut out the piece of fabric. Do this twice.
FLIP THE PATTERN OVER and cut out two more pieces. You should have a total of four pieces.

Tips:

Depending on what kind of "fur" you bought, there may be a natural direction to the grain. Keep this in mind when you're lining up your pattern with your fabric. You want all your fabric fur going the same direction -- probably down.
I tried cutting from both directions, and cutting with the fur facing down was definitely easier.

Step 3: Pin and Sew the Outside Pieces

You now have four pieces of fabric that you're going to sew together into a basic shorts shape. When you're doing this, line up your pieces with the fur-sides facing each other. The icky itchy part should be facing outwards. To sew the outside piece together, you'll sew three seams.

Booty Shorts:

Sew the left and right edges
Sew these front and back edges
Sew the crotch edge

Long Shorts:

Sew the short interior edges
Sew the inside U-shaped edge
Sew the outside edges

Step 4: Attach the Lining

Booty Shorts & Long Shorts:

Turn the shorts you just made right-side-out, and put the original underwear around them so they're perfectly lined up.
Sew the top edges together.
Turn pull the original underwear around so that it's inside the fur lining.
(OPTIONAL) Sew the leg holes in the lining to the outer shell by hand.