Pi Day is March 14: 3.14. To be honest I fall on the cake side of the cake-or-pie debate (also cake in cake-or-death) but every holiday should have a lovely ornament, right?
(A shameless self promotional moment: did you know I have a pattern in a book?)
Pi Day Pin

Delicious but calorie free!
Materials:
Kitchen cotton in a crust color and a filling color
US 5 double point needles
Beads or other decorations as desired
Plastic needlepoint mesh
Felt
Pin back
Fiberfill
Thread
Yarn and sewing needles
Feel free to make whatever substitutions make sense to you. By “kitchen cotton” I mean Sugar n’ Cream or Peaches n’ Creme cotton yarn, or their equivalents. If you use a different yarn, use smaller than recommended needles for a dense fabric.
For fruit pie:
With filling color, cast on four stitches and pull the working yarn all the way to the right, like knitting I-cord.
Round 1: Knit front and back (KFB) into every stitch (8 stitches).
Round 2: Join the stitches for knitting in the round and purl 1, knit 1 (p1, k1).
Round 3: KFB into every stitch (16 stitches).
Round 4: p1, k1
Round 5: k1, p1
Round 6: p1, k1
For a smaller pie, skip now to Round 10.
Round 7: KFB into every stitch (32 stitches).
Round 8: p1, k1
Round 9: k1, p1
Round 10: knit plain
Round 11: Break yarn and join crust color. K2, knit 2 stitches together (K2TOG), (24 stitches).
Round 12: KFB into every stitch (48 stitches).
Round 13: knit plain
Round 14: Bind off in purl.

Fruit pie or double crust pie
Weave in ends and decorate pie top as desired (it’s easier at this point). Turn the pie top over and pick up and knit an even round of stitches, leaving a frill of crust at the outer edge. Knit one round, then bind off and weave in ends.

Sukey supervises…

…and also provides commentary.
Cut a piece of plastic mesh into a circle that will fit into the crust of the pie, and a circle of felt a bit larger than the mesh. Sew a pin back to the mesh and the felt (the felt should be between the mesh and the pin back).
Fill the pie with a bit of fiberfill and fit the mesh-felt-pin back sandwich inside: fit in the mesh, then stuff in the felt as smoothly as possible.
Sew the crust to the felt.
Calculate the value of pi to infinity.
For double-crust pie:
Follow the above directions, using only the crust color for the pie top and sides. While knitting the top of the pie, knit the non-increase rounds plain.

Sukey sez “Cherry? Where’s my lemon meringue?”
Seriously, I have a pattern in a book. Since you’ve been nice enough to read this far, here’s a picture:
Thank you!
How adorable!!!
The kitty you sent me is going everywhere with me on my jacket!