I'm working my way through the original five Percy Jackson books again before the second season comes out on Disney Plus (and before I start Heroes of Olympus). Rick Riordan did a great job remixing Greek mythology in a way that makes me want to know more about the original stories. As I've mentioned before with Doctor Who, that's a hallmark that the story was done well. On the flip side, the Riordanverse seems to love little Easter eggs of turning real world people into Greek mythology. At times we got a snippet of their stories and sometimes just a passing name drop. I'm not sure how many mentions we got in the first five books, but I'll start with six of my favorites and maybe some head-canons.
William Shakespeare, Son of Apollo
Annabeth noted Shakespeare’s demigod status alongside his role as an Underworld judge. How his work as a playwright qualifies him to judge the dead, I have no idea. For hundreds of years, he’s been praised as one of the greatest writers (even if high school students can’t see it). As a son of Apollo, it makes sense that his works would be so well known and widely praised… even if Apollo can’t write a half-decent haiku to save his immortal life. Still, how does writing Hamlet qualify him to judge the dead?
Amelia Earthart, Daughter of Zeus
The famous pilot who flew solo across the ocean and disappeared. A feminist icon. She was mentioned by Annabeth during "Sea of Monsters" in defending herself to Circe. Apparently, she was mentioned again in "The Lost Hero" but since I haven't read that book yet, I'll say no more. As a daughter of Zeus, it makes says that she was a flying phenom. Despite being lost, her story was well known enough among half-bloods that Annabeth didn't feel the need to expand on her mention. I can only imagine that being daughter of the sky and thunder god helped her navigate as a pilot. Makes me wonder how she could have ever gotten lost, but that might be coming in "The Lost Hero".
Harry Houdini, Son of Hecate(?)
Talking to Percy in "The Lightning Thief", a Nereid casually mentions Orpheus, Hercules, and Houdini as half-bloods who managed to escape the Underworld. Acting like Houdini's demigod-ness should be common knowledge, our ocean friend didn't mention whose son he was. Perhaps he was an unclaimed demigod who resided in Hermes cabin. But since Hecate is the goddess of magic and witchcraft, I'm going to guess he's a son of Hecate. But since he was famous for his dramatic escapes (that could have killed him) he could be a son of Hades--He was born long before the Big Three's oath after all. But I'm still going to go with the Hecate head-canon.
Edward Teach, Son of Ares
AKA Blackbeard. Of course the most famous pirate in history is a son of Ares. It’s almost understandable that Circe trapped him, when you think of how Ares and Clarisse love to bully the main characters. That being said, when Annabeth and Percy saves him and the other guinea pigs, Blackbeard and the other pirates made for a good distraction, enabling the escape. And now he can roam the ocean pillaging again.
Harriet Tubman, Daugther of Hermes
With Luke Castellan being the main Hermes demigod in the original five books, his half-siblings can be easily forgotten. His half-sister Harriet Tubman is famous among mortals for saving former slaves. In "Battle of the Labyrinth" she gets a mention by Chiron (hinting that maybe she was at Camp Half-Blood as a youth). It was said she used clear-sighted mortals to assist in her rescue. Chiron hinted that her Underground Railroad may have even utilized the Labyrinth.
George Washington, Son of Athena
The primary historical figure of the American Revolution. Of course Washington was a son of Athena. I’m sure the connection to the goddess of wisdom came in handy during the war and his presidency. His mention in “The Lightning Thief” was another passing reference, alluding to crossing the Delaware. But I would love to learn more about out the Riordanverse side of Annabeth’s half-brother.