Step 3: Sew and Stuff appendages
This part is a little time consuming, but it really brings the hat to life.
Beginning with the teeth, sew the matching pieces together, right sides facing each other, along the long sides of each tooth. Leave the bottom edge of the teeth open. I used a straight stitch.
Turn the teeth right side out.
Line the teeth up along the top edge of one of the jaw pieces, but point the teeth downward. I put tooth 1 in the middle, teeth 2 on either side of that, and the following teeth on the outsides so they'd get smaller as they got farther away from the middle. The piece of jaw fabric should be right side up, and the main part of each tooth should be overlapping that jaw piece, with the unsewn edges of the teeth sticking out along the upper edge. Place the other jaw piece of fabric over this, lining it up with the bottom piece, right side down. Pin this stuff together to hold the teeth in place.
Sew along the top edge of the jaw. You can sew a little farther on either side of the jaw, sewing around the sides and along part of the bottom if you want; this will lessen the amount of hand sewing you'll have to do on this part.
Turn the jaw right side out. The teeth should now stick up nicely along the top edge of the jaw. Stuff the inside of the jaw with some batting, then hand sew it shut. I find it looks best if you fold the raw edges in and use a blind stitch to sew it shut. After you finish stitching it closed, tie a knot close to the stitches, then pass the needle through some puffy part of the jaw, pull the thread through, then snip it off where it comes out. That should leave the tail of the thread inside the jaw and out of sight.
Sew the arms and legs in a similar way; I used a straight stitch around them. I chose a straight edge of each to leave open to turn the appendage right side out. Yes, the fingers are a pain in the butt. You might choose to hand sew those. Stuff them with batting then hand stitch them shut. Note the dotted line in the leg pattern. Use a straight stitch to sew along that line after the leg is stuffed and sewn shut to make an indentation.
The tail has similar dotted lines; treat them similarly. Sew the tail pieces together right sides facing each other, turn it right side out, stuff it, then stitch along the dotted lines to make indentations. I didn't bother to hand sew the edge of the tail.
Sew the spikes with the right sides facing each other. I chose to use the other side of the knit sweater as the outsides for these. Turn them right side out and stuff them. If you want the spikes to be floppy, use batting. I wanted them to stick up, so I used craft foam inside the spikes. I got the shape of craft foam by tracing the spike after it was turned right side out. I used the machine to stitch the bottom edge of these closed, since they wouldn't be visible anyway.
I stitched along the outside edge of the earflaps, leaving the finger edges open. Then I turned those right side out, traced a webbing shape on some gauzy fabric, and machine stitched the finger edges of the ear flaps together with the gauzy fabric sandwiched in between.
The tentacle can just be stitched along the long edge, then turned right side out. You can ignore those little lines on the fatter end of that tentacle. I stuffed the tentacle with two long strips of craft foam.
I forgot to add a shape to the pattern for the globe thing on the end of the tentacle (partly because I was originally going to do an epoxy/glow powder drop instead). Cut a circle out of fabric about as large as the eye socket shapes. Cut four V shapes around the edges of the circle to make a flower-like shape with four petals. Sew the sides of the petals together, so that the flower folds up to form a basket shape. Turn this right side out, stuff it with batting, then gather the opening. Stitch it shut, and hand sew the smaller end of the tentacle to the bulb, trying to make sure the tentacle fabric covers some of the scrunched up folds of the bulb.