OG Monster onesie — olive green with brown hair — Big Mouth Monster Onesie, unisex S-XL

40% OFF

Become the Big-Mouth Monster of the Party 👹

The viral hooded onesie with a giant monster mouth — thick, cozy flannel, and matching monster slippers included. One suit. Big mouth. Zero boring nights.

★★★★★Loved by early customers

$116.65$69.9940% OFF

Pick Your Monster: OG Monster

Size: M

🛒 Add to Cart — 40% OFF Buy Now

🚚 Free shipping over $100
↩️ 30-Day Money-Back
⚡ Fast tracked shipping

👻 As Seen on TikTok

Real monsters, real reactions.

🛒 Get Yours — 40% OFF

Find Your Perfect Fit 📏

Unisex S–XL sizing. Between sizes? Size up for extra roominess.

Big Mouth Monster Onesie size chart with height and weight measurements for sizes S through XL

Why the Big Mouth Monster Onesie hits different

Giant cartoon monster hood that steals every group photo
Thick brushed flannel — warm enough to live in all fall & winter
FREE matching monster slippers with every suit
Unisex, true-to-size fit for men & women (S–XL)
7 monsters so the whole crew can match
Zips on in seconds — costume + cozy loungewear in one

LOW STOCK — selling fast

Why it sells out every year

Every Halloween these fly off the shelf. Limited stock this season — grab your monster before it's gone.

days

hrs

min

sec

Claim My Onesie

Get the crew matching

Mix and match monsters — pick a size for each one.

Onesie 1

Onesie 2

Free shipping unlocks at $100 — the 2-pack gets you there.

🛒 Add 2 to Cart — $125.98

4.9/5

Loved by Halloween fans

Based on 12 verified buyer reviews

Jenna M.

Verified Buyer

5.0

Wore it to a party and got stopped every five minutes for photos. The hood is huge and the flannel is unreal cozy.

OG Monster

Marcus T.

Verified Buyer

5.0

I'm 6'3" and the XL still fits with room. Zipper is smooth, no snagging.

Bigfoot

Priya S.

Verified Buyer

5.0

Bought it as a joke costume and now I basically live in it. The free slippers were a nice surprise.

Purple People Eater

Dylan R.

Verified Buyer

5.0

Shipped fast, quality is way better than the cheap onesies I've bought before.

Frost Bite

Alexis W.

Verified Buyer

5.0

My boyfriend and I got matching ones. Instant hit at the Halloween party — everyone asked where we got them.

Pumpkin Monster

Tommy K.

Verified Buyer

5.0

Warm enough for a cold night out but I didn't overheat inside. Perfect balance.

Hellspawn

Jenna M.

Verified Buyer

5.0

Wore it to a party and got stopped every five minutes for photos. The hood is huge and the flannel is unreal cozy.

OG Monster

Marcus T.

Verified Buyer

5.0

I'm 6'3" and the XL still fits with room. Zipper is smooth, no snagging.

Bigfoot

Priya S.

Verified Buyer

5.0

Bought it as a joke costume and now I basically live in it. The free slippers were a nice surprise.

Purple People Eater

Dylan R.

Verified Buyer

5.0

Shipped fast, quality is way better than the cheap onesies I've bought before.

Frost Bite

Alexis W.

Verified Buyer

5.0

My boyfriend and I got matching ones. Instant hit at the Halloween party — everyone asked where we got them.

Pumpkin Monster

Tommy K.

Verified Buyer

5.0

Warm enough for a cold night out but I didn't overheat inside. Perfect balance.

Hellspawn

Sofia L.

Verified Buyer

5.0

The giant mouth hood makes the whole costume. Photos look ridiculous in the best way.

OG Monster

Chris B.

Verified Buyer

5.0

Ordered a size up like the guide said and it was spot on. No regrets.

Bigfoot

Hannah D.

Verified Buyer

5.0

Washed it twice already and it still looks brand new. No pilling, no fading.

Purple People Eater

Andre P.

Verified Buyer

5.0

Best $80 I've spent on a costume. It doubles as loungewear all winter.

Frost Bite

Mia C.

Verified Buyer

5.0

Pockets are actually deep enough for a phone and keys. Small thing, big deal.

Pumpkin Monster

Nate F.

Verified Buyer

5.0

Won the costume contest at work. Zero effort, maximum reaction.

Hellspawn

Sofia L.

Verified Buyer

5.0

The giant mouth hood makes the whole costume. Photos look ridiculous in the best way.

OG Monster

Chris B.

Verified Buyer

5.0

Ordered a size up like the guide said and it was spot on. No regrets.

Bigfoot

Hannah D.

Verified Buyer

5.0

Washed it twice already and it still looks brand new. No pilling, no fading.

Purple People Eater

Andre P.

Verified Buyer

5.0

Best $80 I've spent on a costume. It doubles as loungewear all winter.

Frost Bite

Mia C.

Verified Buyer

5.0

Pockets are actually deep enough for a phone and keys. Small thing, big deal.

Pumpkin Monster

Nate F.

Verified Buyer

5.0

Won the costume contest at work. Zero effort, maximum reaction.

Hellspawn

30-DAY GUARANTEE

30-Day Money-Back Guarantee

Not obsessed with your monster suit? Send it back within 30 days for a full refund. No spooky fine print.

Questions, answered

What sizes do you have / how does it fit?+

Unisex S–XL, true to size. Between sizes? Size up for extra roominess. See the size guide.

Is it warm?+

Yes — thick brushed flannel (251–300 g/m²), built for cold nights, movie marathons and winter lounging.

Do the slippers really come free?+

Every onesie ships with matching monster slippers, included at no extra cost.

How fast is shipping?+

[State your real processing + delivery time], tracked door to door.

What's your return policy?+

30-day money-back guarantee on unworn items.

How do I wash it?+

Machine wash cold, tumble dry low. Easy.

Don't Be the Only Boring One This Halloween 🎃

Buy Now — $69.99

🚚 Free shipping over $100
↩️ 30-Day Money-Back
⚡ Fast tracked shipping