[1] The concept has been used in science fiction and actual ships[1] such as the Mercury capsule, Vostok and some suborbital designs.
[1] Highly compact single-person spacecraft have been considered by ISS for EVA work, to avoid having to go through the decompression needed to use the lower-pressure space suits.
[9] NASA developed a body-shaped single person spacecraft called FlexCraft, with the idea of allowing more and shorter EVA.
[9] The spacecraft would be at the same atmospheric pressure as the ISS, thus removing the medical stress and time needed to decompress and compress, and the danger of the bends.
[11] This design has a hatch at the bottom that an astronaut could enter into, but it would be at full pressure thus avoiding the need to purge nitrogen from the body for low-pressure suits.