King Rhesus of Thrace was a Trojan ally in Homer's Iliad. His name has been given to a type of monkey from the macaque family, native to Afghanistan, Pakistan, India, China, Myanmar (aka Burma) and a few neighboring countries.
The trivia items below may give away important plot points.
During shooting of the scene where Hercules breaks free of his chains, Dwayne Johnson stated that he "blacked out" after every take: "I asked the prop department to lock me in with real steel chains that I couldn't break, so the performance would be real. When Hercules finally accepts his fate of being the son of Zeus, it's the epic moment of the mythology--and our movie. We shot this scene eight times--I blacked out every time. Down to my knees. Well worth the pain . . . this moment is iconic. I'm excited for you to see it."
When King Eurystheus congratulates Hercules for killing the Hydra, he's shown breeding peacocks. This is the sacred animal of the goddess Hera, Hercules' arch-nemesis--possibly a clue to Eurystheus' true intentions.
In the beginning Reece Ritchie's character is strung up by his arms in a seated position over a torture device called the pyramid, which ends in a sharp point just inches away from the victim's posterior. This was a popular method of torture in those days, as gravity would weigh the victim down and eventually impale him.