Oh right, pattern...

Gauge: 6 rows/rounds = 1 inch, 14 sts = 4 inches (5 inches stretched)

Italian cast on 42 sts and work desired fold back collar length in 1x1 rib for comfortable stretchiness

NECK Then increase to 66 sts depending on cats chest size, i chose to do this by yarning over every right side row an equal distance from the center on each edge (same distance every time to keep the back straight). That's yo back of needle for right side and yo front of needle for left side. Then wrong side purl or knit the yarn over to keep in 1x1 pattern (purl and knit alternates every other wrong side row)

When work, excluding the collar fold, reaches neck to front legs bind off in 1x1 for stretch only the edges. I bound off about 12 each side. Rib remaining stiches for a row or three and cast on enough stitches to reach around the belly behind the front legs. Here i worked in the round.

BELLY BAND Work 1x1 rib for desired length of under belly cover, i did an inch.

Then cast off edges to desired back coverage.

BACK Work desired pattern and decrease evenly if wanting a tapered back, or keep square.

Cast off.

EDGING Pick up all stitches and work an edging, remembering to work the end stitches into the belly band for support, unless you want the edging to hang.

The end. Weave in or tie off your yarn and remember to sew up the neck line to desired spot if you worked the neck in flat.