Measure the distance around the edges your bunny ears and cut two neopixel strips to fit snugly inside. My strips ended up with 20 neopixels each.
Cut carefully through the center of the copper pads, being sure to leave enough pad on each side for soldering.
Find the "in" end of each cut strip (the arrows should be facing AWAY from that end). Solder 3 color coded wires to each strip: red to 5v, black to G, and white to IN.
The wires should be about 5" long for one strip, and about 10" long for the other. We can trim them down later, so when guesstimating lengths, always err on the side of "too long".
We'll call the one with shorter wires strip #1, and the one with longer wires strip #2.
Look closely at your on/off switch. Figure out which end the battery wants to plug into: this is the male end and we'll leave that one alone. Find the other end (the female end) and snip the connector off with wire cutters.
Splice the long red and black wire attached to strip #2 to the red and black wire coming from the switch.
Solder a 4" red and black wire from the OUT end of strip #1 to the OUT end of strip #2.
Test to be sure your connections are good by hooking up some alligator clips to the remaining free wires. Attach BOTH white wires to A1. Then attach the free red wire coming from strip #1 to VOUT and the free black wire to G on the Circuit Playground.
If all your connections are good, the strips will light up when you plug in your battery and tilt the Circuit Playground. Let's secure the ends of the strips so they don't ever pull out or break while you're wearing the ears.
Cut four pieces of 1/4" clear heat shrink and place them over the end of each strip. Before you shrink them down, squirt some hot glue onto the strand to cover the solder connections. Then while the glue is still wet, use a heat gun to shrink the heat shrink down. This will create an indestructible and waterproof seal for your LED strips.
Use a thread ripper to carefully remove both ears from the headband.
Fold the neopixel strip gently in half with the lights facing outwards. Slip the strips up inside the ears to be sure they fit.
Orient the ears so the animation runs from left to right when you tilt the board to the right, and vice versa. Think about how it's going to sit on your head and be sure it makes sense to you. It's easy to get the ears on backwards, so take a minute and be sure you've got things laid out right.
Once you're SURE you've got the layout right, remove the neopixel strand from one ear and turn the ear inside out.
The Circuit Playground needs to be oriented carefully for the tilt sensors to work right. Mark the top and bottom with respect to the ground and sky while the ears are on. Don't just align it with the ear's top and bottom since the ear will be on your head at an angle.
Sew the Circuit Playground onto the back panel of the ear through the unused pads. You can also use your thread ripper to cut a small slit in the back of the ear to make the USB port accessible, in case you want to change or adjust the code later on.
Turn the ear right-side out again and replace the neopixel strip. Stuff the battery inside the opposite ear. Test your orientation again! The Circuit Playground should be on the BACK of one ear and the USB port should be perpendicular to the ground. Be sure the animation on both ears is running in the correct direction.
We'll need to be able to get to the battery for charging. Cut a small hole near the bottom of the battery-containing ear and slip the JST connector through before plugging it into the switch. This way it will be on the outside, so you can easily hook it up to the charger.
Place the switch on the back of the headband between the ears. Stuff the wires inside the ears and sew them to the headband, being sure you can still get to the JST connector.