Drop seat pajamas are pajamas with a flap over the buttocks that the wearer may lower at their discretion. The garments also are known as butt flap pajamas. The primary purpose of the drop seat on this type of pajama is to facilitate easy use of the toilet without removing the entire pajama. This kind of pajama was popular around the 1950s but has declined in use to the point where they are somewhat difficult to find in general department stores. Drop seats are easy to find through online vendors.

The flap of a drop seat pajama typically is held in place with Velcro, snaps or buttons. When the wearer wishes to lower the flap, he undoes these fasteners and lets the material of the flap fall downward. The wearer simply reverses the process to reattach the flap to the rest of the pajama. Snaps are the norm on contemporary drop seat pajamas, as snaps are easier to manage compared to buttons but are more secure than Velcro.

Usually, manufacturers make drop seat pajamas for children, particularly toddlers. Some adult versions are available for both men and women, however. These versions often are purchased for novelty or reasons of nostalgia. In some instances, adult drop seat pajamas prove useful when a person has a medical condition that limits mobility.

Although the main function of drop seat pajamas is to let the wearer use the bathroom, parents also often like drop seat pajamas because they allow the parents to check a child's diaper or pull-up with ease. Parents who support spanking as a method of discipline also sometimes like the pajamas because the parent quickly can expose a child's bottom, although this is a controversial benefit of the garment. Another advantage includes modesty, as the pajama does not require total removal.

Companies who make drop seat pajamas typically use materials like polar fleece or polyester. These materials are more flame-retardant. They are very warm, as well, which is important for small children who may not be ready to use regular blankets. In adult versions of drop seats, however, more variety is found in the material. Some manufacturers produce versions that use only natural fabrics like cotton to meet the needs of those with skin conditions or allergies.

Traditionally, drop seat pajamas are just one color, having no design. One reason for this is that the materials used for drop seat pajamas tend to pill and show wear rather easily, meaning that designs can become less vibrant or clear over just a few washings. Drop seat pajamas are produced in a wide range of colors, and some companies do make versions with designs, particularly if the design relates to a popular phrase, concept or media production. In these cases, the design connects directly to the company's marketing scheme.