Usually I do but I've often wondered. It's suppose to be healthy to get some air down there from time to time and I don't like sleeping naked nor do I wear boxers (boxer briefs) so from time to time I'll sleep in my pj's without anything on underneath.
The wearing of underwear under pjs is a matter of personal preference. They wear whatever is comfortable for them. Then too, it depends on why they are wearing pajamas. Most people here in the west use pjs mainly for sleeping and may or may not wear underwear with them. However there are some cultures that wear pjs as lounging attire at home and these people more than likely would wear underwear beneath the pajama.
As a rule they are required to wear special underwear. However, one needs to make sure that this underwear is seamless. It is not a secrets that jury deducts points if underwear is visible through or under a leotard
strawberry shortcake underwear (:
Yes especially if they for some reason don't have pajamas at all
clean underwear, clean pajamas, and no socks
I prefer underwear, but you can wear either.
Some women wear underwear under tights and some do not. Tights are made to be worn without underwear, but many people do still wear them.
A union suit is a type of under clothing. This is a one piece underwear outfit to wear as nightwear or under clothing in the winter. These are known as footy-style pajamas but without the feet.
Asian ladies can wear underwear under their dresses. Most Asan ladies do not wear underwear.
Some people do, but most people wear underwear.
Not everyone sleeps in pyjamas, some people like to just wear underwear instead.
Underwear is not necessary under leotards, and when it peeks out, it looks unproffessional.