SNUG, warm and resembling an outsized baby grow, they are the unstoppable craze sported by the likes of Brad Pitt and boy band One Direction.
Now a Hampshire school has taken the fashion phenomena onsie step further.
Yesterday pupils and teachers smashed the Guinness World Record for the largest gathering of people wearing the one-piece pyjamas.
Some 1,184 staff and students from Ringwood School had rallied in their treasured all-in-one suits for the challenge as part of an end of term sponsored non school uniform day.
The sea of striped, spotted and multi-coloured onsies broke the record by a comfortable margin of 432 onsies. The school is now awaiting official confirmation of this from Guinness World Records.
Organiser Gemma Diaper said: “I am confident we have broken the record.
“It was quite a sight and certainly broke the usual school uniform rules.
“Some of the children and teachers wore their onsies all day.”
The wacky record bid also raised £1,200 for Rotary’s End Polio Now campaign and various cancer charities. This included Families Against Neuroblastoma.
The school decided to raise money for the charity to pay tribute to four year old Henry Allen from Buckinghamshire, whose tragic death inspired the last onsie record breaking event in Milton Keynes last November.
That attempt saw 752 people turning up to break a world record.
The day before hundreds lined the streets to help say goodbye to the brave youngster, who passed away on October 20 after suffering with Neuroblastoma, a childhood cancer.