In 2269, the Excalbians became intrigued by Human notions of good and evil. They staged a contest between the two concepts, using Captain Kirk and Commander Spock of the USS Enterprise, and recreations of notable galactic historical figures.
Representing "good", were Kirk, Spock, Abraham Lincoln of Earth and Surak of Vulcan; representing "evil" were Kahless the Unforgettable of Qo'noS, Genghis Khan, Colonel Green of Earth and Dr. Zora of Tiburon. (TOS: "The Savage Curtain")
Information about Excalbians was displayed on a computer graphic in Keiko O'Brien's classroom on Deep Space 9 in 2369, as a part of her lesson on comparative xenobiology. (DS9: "A Man Alone", "The Nagus")
The Pocket TOS novel Savage Trade has the Enterprise encountering a group of renegade Excalbians who wish to apply for refugee status to the Federation. They were forced to take permanent human form, again notable members of Earth's history.