When Hercules and his group visit the Saran, two steel bars suddenly appear and block the doors. But the bars are then missing in all subsequent shots until they reclose at the end of the scene.
The U.S. English language version has some major errors in the opening credits. Director Pietro Francisci is named Francisici, and the beautiful Fulvia Franco is credited Fulvio Franco, as if she was a man.
When Hercules kills a feral bull, in that coastal oasis following their shipwreck, he and his fellow castaways keep mentioning that they've never seen such a strange animal. But, that its meat is delicious. This contradicts classical Greek mythology which is filled with more than one myth about Hercules wrestling and/or killing angrily charging bulls. Plus, Homer's Odyssey lists the House of Laertes as owning twelve herds of cattle! So, both Hercules and Ulysses should've easily recognized this animal as a wild bovine.
Obvious stunt double for Kirk Morris during the fight scene with the lion.
Power lines visible in the background of some scenes.
The helmets of the Roman soldiers are actually disguised World War II German army helmets.
Samson lived about 1100 BCE, Ulysses about 1200 BCE, and Hercules about 1250 BCE.
If you look closely at the boulders thrown down at the Philistine army by Hercules and Samson, you can see that they are all duplicate from the same two molds.
Samson has short, obviously styled, hair.