This doll is part of the PeeWee series that was made by Uneeda during the 1960's and 1970's. The box says this doll was made in 1973. Some of the PeeWee dolls were standup dollies and others were bent knee babies. This is one of the babies. She has a cute playsuit with a ruffled rumba rear: which explains the Fancy Pants name.
The Fancy Pants dolls were made in a variety of sizes. This was most likely the smallest size. So this particular doll is actually part of TWO collectible series.