Summarize the following:
Make sure it is longer than your height from head to toe and wide enough to wrap completely around yourself with a good amount of extra space. . Measure your fit against a comfy pair of sweats and a hoodie. Fold them lengthwise and cut on your folded fabric, leaving about 1.5 in (4 cm) for seam allowance, then flip them and repeat to cut out the back of your onesie. Sew on your zipper, then cut out and sew on your sleeves. Fold your sweatshirt in half on an unused, folded section of your fleece. Trace it or pin it in place, then cut around it, leaving about 1.5 in (4 cm) for seam allowance. Sew the two pieces together on the curved edge. Open the hood and pin its bottom portion to the back collar of the onesie. Sew it into place. Choose a complementary felt color, such as pink for a white or gray costume, or white for a pink costume. Measure yourself from chest to waist, then cut out an oval of that length. Cut it in half, then use a sewing machine or fabric glue to affix the pieces to either side of your zipper. Cut out two long ear-shaped pieces of matching felt, then two smaller inner ear pieces out of your complementary color. Glue or sew the inner ears onto the bigger ones. For floppy ears, simply glue or sew your felt pieces directly onto your hood. For ears that stand up, attach pipe cleaners or thin wires to the back of the ears, following the edge of the felt. Glue or sew a strip of felt over the wire or pipe cleaners to hide them, then attach the ears. To add the finishing touch to your bunny onesie, use handful of small white cotton balls, one large cotton ball, or a bunched-up feather boa that matches your chest piece and the insides of your ears. Attach it to the back of your costume using fabric glue and let it dry overnight. For added security, clip it on with a few safety pins once it's dried.

Summary:
Start with a large cut of pink, white or gray fleece fabric, or a fleece blanket. Make your onesie Cut and sew your hood. Make a chest piece. Add a pair of bunny ears to your hood. Make a bunny tail.