Big Mouth: The ghost of Duke Ellington haunts the attic of the Birch family house, where he died. Fortunately, he's a congenial sort who dispenses useful life advice (and, admittedly, a fair few unhinged Conspiracy Theories) and takes holidays in town. A flashback focused on him reveals that he also had a ghost when he was a kid: Harriet Tubman.
The entire premise of Clone High was this. Take as many historical characters as possible, clone them, put the clones in a high school setting, and Hilarity Ensues.
Several minor characters in Futurama, though mostly as only as heads in jars. The most commonly recurring character, with roles in the plot, is Richard Nixon.
Besides King Richard I and Prince John, Ivanhoe: The King's Knight also features Alexander II of Scotland as a prince and Inge Magnusson.
Many bit part and recurring characters in Liberty's Kids.
Molly of Denali: Walter Harper and the other members of the Stuck-Karstens expedition in the special "Molly and the Great One." Though they're only seen in flashbacks, intense details of their expedition are shown, including a fire at base camp that destroyed most of their gear. The kids latch onto Harper and a teenager named John Fredson, the latter a Gwich'in boy responsible for caring for base camp completely alone, treating them as their personal heroes.
In allthreeiterations of Mr. Peabody & Sherman, the world's smartest dog and his boy are time travelers who interact with historical figures on a regular basis.
Filmation's The New Adventures of The Lone Ranger incorporated a bit more historical old west characters in order to give it a slightly educational context.
Pirate's Passage features Captain Charles Johnson (Daniel Defoe if you subscribe to the belief they are one and them same), Calico Jack and Anne Bonny.
Time Squad is about a small police unit traveling through time making sure famous people do what they're historically famous for — if Copernicus ever forgets the Sun existed or George Washington Carver manifests an Evil Twin, the Time Squad will be there to fix it.on
Xavier Riddle and the Secret Museum: Xavier, Yadina, and Brad often go back in time and meet famous people of history when they were children, such as Rosa Parks and Leonardo da Vinci, who help them learn important lessons.
