Teen entrepreneur Mary-Kate Olsen loves to buy big, stylish jackets, because then she can secretly wear pyjamas in public.

The 19-year-old beauty, twin sister of Ashley Olsen, often goes out with her nightwear on, and she keeps it all hidden under her over-sized coats.

She says, "I love getting amazing jackets because you can wear your pyjamas underneath and everyone's like, 'Oh, fabulous jacket,' and I'm like, 'You should see what's underneath!'"