Forget Godzilla, it turns out the kigurumi is the Japanese fashion monster currently invading our towns and cities. In Japan the word refers to the costumed performers who dress up as cartoon characters, particularly animals, such as might be seen parading around at a theme park or shopping centre. These outfits were then subsumed into Japanese street fashion and worn in a non-commercial capacity.

The trend spread out of Japan to the UK where in 2009 the Kigu brand was started. Their online store stocks the usual suspects you might have seen on the street like penguin, cow and tiger onesies, but also extends to the more exotic options of pugs and lemurs. The brand marketed their product to festivalgoers as a comfy costume clothing hybrid and soon a craze was born. This year the company is on track to make a rather staggering NZ $3.8 million turnover.

And the fad to wear these animal onesies out and about seems to be spreading faster than frozen yoghurt shops in an inner-city neighbourhood. Now we'll admit there are some things that segue from festival wear to streetwear chicly. Embroidered dresses, slouchy boots, baseball caps. The basic rule is, can you imagine Kate Moss swanning around Primrose Hill in it? Animal onesies do not fall into this category.

The kigu fashion plague is plain baffling. After all they're not especially flattering. You can't easily go to the toilet in them. Oh, and you're dressed as a giant penguin, there's also that. But the trend seems to keep gathering momentum with animal onesies now stocked in mass market, Gen Y targeted fashion chains like ASOS and Urban Outfitters. Nightclubs are now hosting onesie parties (dress code: no onesie, no entry).

So how did they cross over from obscure Japanese fashion subculture and festival attire to having actual allowed-to-vote adults feeling comfortable walking down the street masquerading as a lion? Why are lambs literally dressing as mutton? Well, the animal playsuits got the celeb stamp of approval in a big way. Lily Allen appeared in public dressed as a dinosaur and the Pink Panther. Model Cara Delevingne is quite the aficionado (she's been a panda, tiger and monkey) to the point where she even joked on Instagram that she should start her own onesie line.

But probably the tipping point moment was the viral video posted of Miley Cyrus twerking. If you haven't seen it, it's a YouTube hit with 1.6 million plus views featuring a lone unidentifiable figure twerking in a unicorn onesie, who in the final seconds of the clip pulls down her onesie hood to reveal Disney dropout, Miley. So scandalous. It's not surprising the vid went viral given it hit the cultural zeitgeist jackpot by featuring both the animal onesie and the sexy dance du jour, twerking. If only Miley had been eating a cronut at the same time she'd have hit the trend trifecta and YouTube would've imploded. The clip brought the fashion trend to a much younger, more mainstream audience.