1 yard 60 wide fake fur
1/4 yard pink felt
2 2 pieces of sticky back velcro
Step 1: Measure Roomba
Step 2: Make patterns
When I was making the mouse, I didn't bother with making patterns for the top and sides at all - I just drew and cut directly from the Roomba itself (see Step 3).
Cut whatever pieces you've made out of whatever kind of paper you're using.
Step 3: Transfer patterns to fabric
As I said, I didn't bother using a pattern for the top and sides since they're very simple shapes. I just put the Roomba down on the fake fur and traced its edge using a piece of white soap. White soap (pale chalk or brightly colored gel pens also work well) is good for marking up dark fabric. And there you have the top of the mouse.
Then I measured around the edge of the drawn circle using, um, a USB cable (I didn't have measuring tape handy). Using a ruler, I sketched out the dimensions for the side of the mouse - a rectangle as high as the Roomba and as long as the Roomba's perimeter. Here's where things get a bit complicated. Depending on what kind of fabric you use, there may be a discernable direction to the way the fabric lays. This is pretty obvious on fake fur - when you 'rub it the wrong way,' you can tell. I wanted to make a mouse whose fur went the right way. So I drew the side rectangle so that when cut out, the fur would look as if it flowed naturally from the top of the mouse to the floor. This should make sense if you refer back to the mouse picture in the intro.
The tail is another rectangle - this one much skinnier. I sketched mine out freehand and placed it so that the fur flowed from the base of the tail to the tip.
There are two ears, and each ear has an inner (felt) and outer (fur) piece. Note that the pattern (seen below) was slightly asymmetrical, because I wanted the ears to be slightly cocked to the side. Get two small squares of fur and lay them down so the fur is facing the floor. Put the ear pattern down right side up on one piece of fur and draw around it with the soap. Then flip the ear pattern over and put it on the second piece of fur. Draw around it. Now you will have two fur ear pieces, one a reflection of the other.
The pink felt is easier to cut. Take one piece and fold it in half. Lay ear pattern down on the folded felt and trace it in dark pen. Keep the felt folded - when you cut that pattern out, you will get two felt fur ear pieces, one a reflection of the other.
You only need to cut out one nose - it's just a small oval of felt. I have drawn nostrils on the pattern so that you can see how they would go - but I didn't choose to use them on my version of the mouse.
Step 4: Cut out pattern pieces
Some of the pieces will need some extra room outside of the traced pattern. This is called the seam allowance. You can leave as much seam allowance as you want, but I usually go with one-half inch. In this case, I have marked the areas that need a seam allowance of some sort with a thick black line on the pattern reference. On those sides, cut one-half of an inch outside of the traced pattern line.
Only applicable if you are using very thick fake fur: Go back and trim the fur from the seam allowances. This will keep the seam from being too bulky later on.
Step 5: Sew tail together
Step 6: Sew top and sides together
Before you start sewing, you might want to cut little triangles out of the circular top as shown in the photo. This is called "clipping." The idea is to make the triangles big enough so that they almost - but not quite - touch the seam line that you drew from the pattern. You place them every couple of inches to reduce the bulk of the fabric.
Take the tail piece you just stitched together and pin the "bottom" of it to the non-fur-side of the top so that there's about an inch of tail inside the seam line. That way, when you sew the sides onto the top the tail will already be placed where it needs to be.
Usually, one would begin by sewing the ends of the side together to make a big circle, fitting the top into the circle, and pinning them together so that the seam of the side matches up to the bottom of the tail.
However, if you are using the Roomba hack from Tod and Mike, then you will probably want to leave a slit open for the Roomba controller to stick out. So I left the back slightly open by not sewing together the sides first. I still pinned the side to the top so that the slit was at the bottom of the tail, though. See the picture of the inside-out Roomba cover for details.
Now would also be a good time to check if the base fits.
Step 7: Sew pink felt onto ears
Cut a slit from the base of the fur piece to the bottom angle of the felt piece.
Step 8: Attach ears to costume base
Now take one of the ears and pin it to the "face" of the Roomba at whatever angle you think is cutest - or creepiest. Refer to this and this if you need any inspiration. The slit you cut in the base of the ear should make two flaps you can pin flat to the "head" of the mouse costume at the appropriate angle.
Stitch the ears onto the mouse. If you have chosen long fur, it will nicely cover all the visible stitches.
Step 9: Make snout
Step 10: Sew on the little pink nose
Step 11: Attach whiskers
You're almost done. I promise. Just one more thing.
Step 12: Velcro stickums
Peel off the paper backing from one side of the Velcro pieces. Stick them onto the Roomba somewhere where they won't interfere with the buttons. Now peel off the other side and place the costume down on the Roomba. Press firmly to attach the velcro to the costume.
Now your cleaning machine is unstoppable. Except when the battery runs out.