Cosy Never Looked This Fun
Meet your new cosy-night essential. Made from ultra-soft, thick coral fleece, our Big Mouth Monster Onesie wraps you in warmth while keeping things fun. The relaxed oversized fit gives you plenty of room to move, while the character hood and pocket add a playful finish. Perfect for lounging, sleepovers, movie nights and chilly mornings — once it’s on, you won’t want to take it off.
Comfort With Character
Cosy doesn’t have to be boring.
Our Big Mouth Monster Onesies combine ultra-soft coral fleece, oversized comfort and playful character details for the ultimate stay-at-home uniform.
Made for movie nights, sleepovers, chilly mornings and lazy Sundays, they’re warm, roomy and ridiculously fun to wear.
Get cosy. Get comfy. Get silly.
Results
Side effects of slipping into a Sunday Sleeper Monster Onesie may include extreme cosiness and questionable behaviour.
100%
more likely to cancel plans and stay on the couch.
98%
Increase in unnecessary dancing around the house.
99%
chance someone will ask, “Where did you get that?”
What Customers Are Raving About!
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“I bought this thinking it would be cute for movie nights and now apparently it’s my entire personality. So ridiculously soft and warm and the oversized fit is perfect.”
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⭐⭐⭐⭐⭐
“My kids absolutely LOST IT when I walked out wearing this 😂 It’s honestly way softer and cosier than I expected. I’ve worn it nearly every night since it arrived.”
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“Zero regrets. I look completely ridiculous and I’ve never been more comfortable. Super plush, roomy and actually really warm. Already ordering another colour.”
Our Guarantee
We want you to love your Sunday Sleeper. Every order is covered by our store policies, and our customer support team is here to help if there’s an issue with your order.
Frequently Asked Questions
FAQ
What size should I choose?
Our onesies have a relaxed, oversized fit. We recommend choosing your size based primarily on height using our size guide. If you’re between sizes or want an extra-slouchy fit, size up.
Is the onesie unisex?
Yes. The relaxed oversized design is made to be worn by anyone who wants to be ridiculously cosy.
What is it made from?
Made from thick 251–300 GSM coral fleece, giving it a plush, soft and warm feel that's perfect for cooler weather.
Is it actually warm?
Yes! The thick fleece is designed to help keep you cosy through autumn and winter without sacrificing that soft, snuggly feel.
Can I sleep in it?
Absolutely. Wear it for sleeping, lounging, movie nights, sleepovers, lazy Sundays or just because you can.
How do I wash it?
Machine wash cold on a gentle cycle with similar colours. We recommend air drying or tumble drying on low to help keep the fleece looking and feeling its best.
How fast is shipping?
How do I get in contact?
Complete Your Sleep
Experience the comfort of a luxury hotel every night. Our premium pillows are designed to provide cloud-like softness, gentle support, and the perfect balance for deeper, more restorative sleep.