I discovered that I had 3 pairs of little boy pants with holes that were perfect candidates. The first pair I tackled had (impressive) holes in both knees. This called for matching patches on both legs, sewn on with a couple quirky rows of zigzag stitches.
What I did was figure out the length and width of the patch required, add a couple inches to each measurement, and then cut 2 pieces (per leg) of my patterned cotton fabric. To make sure the patch was going to hold up to more little boy shenanigans, I also cut a piece of Peel n Stick Fabric Fuse the same size for added strength. This product is sticky on both sides so I took my pieces of cotton and stuck one (patterned side out) on each "sticky" side. That created a really sturdy "double-sided" patch. I pinned the patches on both legs to be even with each other and did a few rows of zigzag to secure them.
I learned a few things from this initial project:
1. The Fabric Fuse was REALLY sticky when my needle was trying to sew in-and-out of it. My needle built up a nice layer of glue that I would clean off every so often and resume my sewing.
2. Sewing a patch on a little pant leg can be really frustrating because something so small doesn't leave much room for maneuvering.
3. It is best to use a larger needle when doing this type of sewing. I used one specified for denim and it worked great.
The next pair had a smaller hole on just one leg. Because the hole was small I didn't feel the need for the Fabric Fuse. I just cut 2 pieces of cotton to size, sewed them right sides together around the edges, and left a little opening to turn the patch right-sides out. Then I pinned it in place and sewed it around the edges with a straight stitch. Super-easy!
I started by cutting some red fabric and making a patch with the Peel n Stick Fabric Fuse like I did on the first one.
With pants still inside-out, I took 6 strands of embroidery thread and a larger hand-sewing needle and stitched around the drawn circle. I turned the pants back right-side out (admired the new monster mouth) and set them aside.
I took some white and black wool felt and hand-stitched some cute monster eyes and then found a good spot for them above the mouth. I secured those with hand-quilting thread.
My monster may not be as complicated as some I've seen, but I was going for one with "homespun" charm. :)