No single-person EVAs were ever done on Shuttle and to date, have not been done from the US side of the ISS.
The only 3 person EVA in history was on STS-49.
It was unplanned and in response to difficulties encountered grappling the satellite they were attempting to repair.
There is a good, detailed writeup in Walking To Olympus starting on page 88. Here's part of it.
While controllers on the ground determined if Endeavour had enough
propellant to carry out a third rendezvous, the crew proposed
capturing the satellite using a three-person EVA (the first in
history) and components of the ASEM experiment payload. The ASEM
struts would be assembled into a triangular structure to which the
three EVA astronauts could attach their feet. Endeavour would maneuver
under Intelsat VI and the astronauts would grasp the satellite with
their hands. Astronauts Story Musgrave, Richard Clifford, and James
Voss used the WETF to test whether three astronauts could fit in the
airlock at once and to determine positioning in the payload bay for
the capture. Meanwhile, the Intelsat organization verified that the
satellite’s surface temperature would not exceed the 160 deg C (320
deg F) glove touch temperature limit, and engineers from Hughes, the
maker of the satellite, determined the best grab locations. At one
point on May 12, seven EMUs were being used simultaneously: three in
Endeavour’s airlock, three in the WETF, and one in a NASA JSC vacuum
chamber. On this date, Kathy Thornton helped Akers, Hieb, and Thuot
suit up, and the astronauts commenced the 100th EVA in history. By the
time they were finished, it was also the longest EVA in history.
(Longest EVA was later claimed by STS-102)
- ASEM - Assembly of Station by EVA Methods
- WETF - Weightless Environment Training Facility