A half slip makes a whole outfit

Floral Petticoat adds some fullness
to the full circle skirts that Barbie has,
but the skinny slip from Fashion Undergarments
cannot be worn under her tight skirts.

We've all seen Barbie and Skipper redressed in their outfits, and we've seen photos of the different types of underwear they've had over the years.  What I've never seen, however, is what the slips look like when worn underneath the dresses.  I am going to show you seven examples of Barbie and Skipper flashing their half-slips.
Barbie first got underwear in 1960:  #919 Fashion Undergarments, with a straight half slip with two rows of ruffles; and 921 Floral Petticoat, a wide half-slip.  I own both of these.
I also own Barbie's half slips from 1969 and 1970.  Skipper had three that I know of between 1964 and 1988.
The slips also came with other items such as panties, girdles, bras, stockings and even shoes.  I don't own all of these and I am focusing just on the slips, so the accessories aren't being included in the photos.  Some of the dolls are wearing the underpants as well, even though you can't see them.
There have been plenty of other Barbie lingerie sets made over the years, particularly in the 1990s, but I don't own most of them and so am not listing them.
My dolls and what they are wearing are:

Barbie

1960 blonde #4 Ponytail Barbie in #978 Let's Dance and #921 Floral Petticoat
1960 black-haired #4 Ponytail Barbie in #981 Busy Gal, holding the slip to #919 Fashion Undergarments
1969 Hair Fair Barbie head on a Twist N Turn body in #1868 Happy Go Pink and #1864 Close Ups
1970 Twist N Turn PJ in #1456 Dreamy Blues and pack Perfect Beginnings

Skipper

1964 brunette straight leg tan skin Skipper in #1904 Flower Girl and #1900 Underpretties
1979 SuperTeen Skipper in Fashion Collectible #2807 fuchsia blouse and skirt and Fashion Collectible #2808 slip and camisole

Skipper in Flower Girl and Underpretties, all from 1964;
Homecoming Queen Skipper in her original gown
and a Lookin' Lively set, both from 1988;
and SuperTeen Skipper in two Fashion Collectible sets, all from 1979

The ruffles to Perfect Beginnings and
Close Ups match the outer garments,
Dreamy Blues and Happy Go Pink, almost perfectly.

1988 Homecoming Queen Skipper in her original gown and Lookin' Lively #2593

Not wanting their minidresses to expose too much
if there is a gust of wind,
Barbie and PJ will also put on half slips underneath.

The crinoline that came with Lookin' Lively
is the stiffest petticoat Mattel has ever made.
Skipper also wears the pantyhose and underpants that were part of the set.