There are a few different materials that friend pyjamas can be made from, but the most popular and most comfortable option is definitely cotton. Cotton is a soft, breathable fabric that will keep you cool and comfortable all night long, and it's easy to care for, so you can just throw your pyjamas in the wash and have them ready to go for your next sleepover. Another popular option for friend pyjamas is flannel, which is also soft and comfortable but has the added benefit of being a little bit warmer, so it's perfect for chilly nights.