I threaded up my sewing machine and overlocker, first with white, then with hot pink, and made myself these loose fitting pyjama trousers based very loosely on the New Look 6216 trousers.
(PJ bottoms regularly wear out so new ones are needed).
In each case I omitted the pockets, generally cut them a bit wider (I like a looser fit for sleeping) and added a combo elastic and drawstring to the waistband (which come out of working buttonholes).
As you can see I went for fairly fun fabrics.
Far left - novelty polycotton with cartoon whales, sea turtles etc.
Centre left - novelty panda fabric (which didn't get used in the black and white quilt). This has stars for the waistband, and I think I might add them as cuffs too.
Centre right - hot pink sheeting remnant, far too bright a colour for me, but fun for PJs.
Far right - purple and green striped shirting. This is the from the remnant left over from a blouse I made in 2009.