Louis quipped: "Harry likes to be naked all the time. He got a hefty fine in Sweden for walking around butt naked."
Harry added: "I did, yeah ... And then in Amsterdam, we hired these little boats and I got told to get out by the owners because I didn't have any clothes on."
Zayn explained: "He really likes being naked in general. He just likes taking all his clothes off. Totally, completely butt naked."
But Louis admitted Harry is not the only member of the boy band who likes to get naked, as all five singers - whose debut album 'Up All Night' went straight to number one on America's Billboard 200 album chart last month - recently went commando while they enjoyed a day of surfing.
During an interview in Australia - where the 'What Makes You Beautiful' hit makers are currently touring - Louis added: "Genuinely, ask anyone. We went commando the other day while coming out of surfing."
An insider said: "She's already doodling baby names on scraps of paper. She's been bragging about how beautiful their children will be because Taylor is so handsome.
"She wants everything with him - love, marriage and a family. But she's set on becoming a mother before they think about anything else and she's talking about giving birth in the next year."