At one point, Grumio asks Marcus what's for dinner. The first food item Marcus mentions is potatoes. The series is set in 27 B.C., at least 1500 years before potatoes were introduced into Europe.
Stylax asks Cynthia to lean forward an inch so the three guys can compare her to the image on the erotic vase. An inch was not a unit of measurement in Ancient Rome.
Reference is made to potatoes, these wouldn't come to Europe until the 16th century.