Novelty character mug cozies are one of the most-requested Halloween crochet projects every year, and almost all of them share the same trick: take a plain ribbed tube — exactly the everyday mug cozy pattern on this site — and add two or three small felt or crocheted features that turn it into a face. This version is an original one-eyed monster, friendly rather than frightening, sized for a standard 11–12 oz mug.

Abbreviations

ch — chain
sl st — slip stitch
sc — single crochet
BLO — back loop only
st(s) — stitch(es)

Materials

Worsted weight yarn in a monster color (green, purple, or any bright shade) plus small amounts of white and black for the eye
5.0mm (US H-8) hook
One button, ¾–1 inch
Small scraps of felt or contrasting yarn, for teeth and horns
Yarn needle
Fabric glue (optional, for felt pieces)

The base cozy

Work the mug cozy pattern exactly as written, through the button loop and final round, in your chosen monster color. This gives you the same ribbed tube, sized to fit a standard mug, as the base to decorate.

The eye

In white, make a magic ring, then work 6 sc into the ring. Join the round with a slip stitch to the first sc. (6 sts) You should have a small, snug white circle with no visible gap at the center.
Work an increase (2 sc) into every one of those 6 stitches around, then join with a slip stitch. (12 sts) The circle will roughly double in width and start to sit flatter, which is what you want for a button-backed eye.

Fasten off, leaving a tail long enough to sew the eye onto the cozy later. For the pupil, cut a small black circle from felt, or crochet a tiny 4-round black circle using the same magic-ring-plus-increase formula at a smaller scale. Position the pupil slightly off-center, not dead-center, on the white eye, then glue or sew it in place: an off-center pupil is what makes the finished eye read as googly and characterful rather than flat.

Horns (make 2)

Chain 6 to start each horn. Work 1 sc into the 2nd chain from the hook, then 1 sc into every remaining chain across the row. Fasten off, leaving a tail at both the start and end of the strip so you have yarn to tack it down with later. Once both horn strips are made, curl each one gently between your fingers into a small C-shape and tack it in place along its curled edge with a few small stitches, so the curve holds and the horn stands up rather than lying flat.

Teeth (make 2–4, felt or white yarn)

Cut small triangles from white felt, roughly half an inch tall, or work tiny 3-stitch single crochet triangles in white yarn. These sit along the top edge of the cozy's front, evenly spaced.

Assembly

Work the pieces onto the base cozy in this order, checking placement against the mug before you commit to sewing each one:

Eye first. Pin the eye to the front of the cozy in the upper-middle area before sewing, then sew it down. Placing it slightly off-center (rather than dead-center) reads as more googly and less symmetrical-doll-face.
Horns next. Sew or glue the two curled horn strips to the top edge, one on each side of the eye, angled slightly outward so they don't flop forward over the face.
Teeth after that. Attach the felt or crocheted teeth along the top front edge, between the horns, pointing downward so they read as a row of small fangs peeking over the rim.
Button last. Sew the button on exactly as the base mug cozy pattern describes, on the flap opposite the button loop, so the cozy still closes and fastens around the mug correctly.

Step back and check the whole face on the mug before trimming any tails: a lopsided eye or a horn sewn too far forward is much easier to unpick and resew now than after everything is finished.

Variations on the theme

Ghost version: skip the horns and teeth entirely, keep the base cozy in white or cream, and add two small black felt dot eyes and a small oval mouth for a simple, friendly ghost face — the same yarn-tassel-ghost aesthetic (button eyes on a plain pale shape) that shows up throughout Halloween craft traditions.
Pumpkin version: work the base cozy in orange, then add a small green chain-stitch "stem" sewn to the top edge and simple triangle felt eyes and a jagged mouth for a jack-o'-lantern face.
Two-eyed monster: work a second eye at the standard 12-stitch size, positioned level with the first, for a more conventional (if slightly less charmingly lopsided) monster face.

Frequently Asked Questions

Can I make this without felt, using only crochet? Yes — every felt piece here (teeth, pupil) can be replaced with a small single- or double-layer crocheted shape in the same rough size; felt is simply faster for tiny, flat details like these.

Is this pattern good for a Halloween craft fair or bake sale table? Yes — novelty mug cozies are consistently one of the better-selling small handmade items at seasonal craft fairs, since they're inexpensive to make, quick to produce in batches, and read as a complete, giftable item rather than a raw material.

How do I store it between Halloweens? Store flat with the other pieces (horns, felt teeth) tucked inside the tube rather than loose, in a bag or box away from moths if any wool is involved — the same storage approach as the Christmas ornaments on this site.

If a full seasonal set appeals more than one mug cozy, the Christmas ornaments post covers three more small novelty projects built the same way — one base shape, dressed up with a few small added details.