Pyjama Party Lifehack:
The easiest solution to pyjama pants dropsy is a pair of suspenders so that your waistband can be loose but stay put for your lounge wear.
They can be as simple as you wish. You can buy a pair with clips so that you don't need much preparation. I made a pair out of three large safety pins and a length of some nice bulky soft yarn.
Here's how:
Use one pin for the centre of the back of the pyjama bottoms.
Use one pin for each side of the front.
Pass one end of the yarn to through the loop of the rear pin. Knot it so that it stays in the middle.
Pass each end through the loops of each of the front pins and tie. The yarn will now have the shape of a 'Y' with pins at each end and the middle.
Let the yarn hang over each shoulder to support the pyjama pants comfortably. Adjust the length to 'suit' yourself. (That was intended as a bad pun.)
Good luck.