Simplicity 9900, a men’s and boy’s pajamas pattern, is what I used to construct this make. My son needed a new pair of pajamas, and this pattern was the ticket. I’ve made this type of pattern many times before in it’s various incarnations of a basic night shirt and pants, to the point where I no longer need to use the instructions – I know them by heart. I made these in a cotton/polyester (60/40) blend jersey, which is what my son requested. Jersey knit has gained popularity in nightclothes and bed linens in recent years, and he prefers it over the traditional woven cotton.