Renée O'Connor actually injured her ankle for real. This is acknowledged in the closing credits disclaimer.
Pheidippides was a real person who ran 246km (153mi) from Athens to Sparta in a day and a half to seek aid against the Persians before the Battle of Marathon. His run is the inspiration for the modern "Spartathalon" ultra-marathon held annually in Greece.
Xena amps up her kill count in this episode.
Dorian and Pheidippides are the only guest characters with speaking parts.
The flail that Xena uses is a peasant weapon, and based on an agricultural tool. The type seen, with a small mace head attached to the chain wasn't used for another millennium, at least.