Here's how I applied a bit of topology to attach the feet to the "Tux" penguin pattern from http://www.free-penguin.org, minimizing the hand-stitching required to finish the project.  This may be a bit difficult to follow, since you can't see me waving my hands.  I'll try to make it clear with diagrams shaded to indicate "inside" and "outside" fabric surfaces.  In all cases here, "inside" is used to refer to the side of the fabric that ends up hidden inside the penguin, and "outside" to refer to the side that's showing.  If the fabric has a nap or other texture on only one side, you probably want that to be on the outside of the penguin.

In the diagrams, this shading will indicate the "outside" of the fabric used for the penguin body.  This shading with stripes  will indicate the "inside" of the penguin body fabric.  This shading  will indicate the "outside" of the fabric used for the penguin feet.  And this shading with stripes  will indicate the "inside" of the feet fabric.

Each foot is made from two pieces of fabric of the same size and shape, attached to the body.  If you look at how the pieces will end up, you will have the outside of the body facing the outside of one foot piece, and the inside of that foot piece facing the inside of the other foot piece.

Start with the body piece and the foot piece that will be attached to it.  Pin them together as they should end up, with their "outsides" together; the body "outside" and foot "inside" will be facing you.  Using chalk or some other soft marking tool, mark a circle on the fabric roughly 3 cm or 1 1/4" in diameter, centred in the rounded part of the foot piece.  Stitch along that circle, then cut a hole through the two fabric layers inside the circle leaving only a narrow margin (perhaps 4 mm or 3/16", or even a bit less if you can do it without cutting the stitched circle and if the fabric doesn't tend to unravel easily).  Remove the pins.  Depending on your fabric, you may also want to do something to finish the cut edge of the fabric to prevent it from unravelling.  The result should be like this:

Invert the foot through the hole, and smooth out the fabric as well as you can.  It will probably be a bit crumpled and bunched together at the hole, since the cut edge of the fabric around the hole is smaller than the stitched circle.  You should have the "insides" of the two pieces together, with the cut edge of the hole between them; the body "inside" and the foot "outside" will be facing you:

Put the second foot piece on top of the first foot piece, "outside" to "outside", the second piece's "inside" will be facing you.  You may wish to pin them together.  Stitch the foot pieces together around the outside edges -- just the foot pieces, not the body fabric!  Again, you may wish to finish the cut edges of the fabric; remove the pins if you used them.  This should be the result:

Finally, invert the foot back through the hole.  Result: all the outsides are outside, all the insides are inside, all the fabric edges are likewise inside.  When you stuff the body of the penguin, you can also stuff the feet through the holes.

jpolowinXYZZY@sympatico.ca but remove the XYZZY - it's a little magic to baffle the spambots.