Character mistake: Throughout the series, General Ross refers to Gabe Jones as Gabriel. Someone of Ross' military credentials would not address another government agent by their first name. He would call him Agent Jones or simply Jones.
Armageddon Now: Part 1 - S4-E13
Character mistake: Callisto's sword is missing. When she appears in the Xena Season Three finale "Sacrifice", her sword has reappeared. It is never explained why Callisto doesn't have her sword during her three appearances on Hercules the Legendary Journeys.
The Hairy Scare of the Devil Bear - S1-E8
Character mistake: Velma says bears only have four claws. Wrong, they really do have five claws.
Character mistake: Jessie's dance moves don't match what the other girls are performing, even though it's a choreographed routine.
Proof Through the Night - S1-E4
Character mistake: Dominic said the MIGs were coming in 015° but the readout says 105°. If they were at heading from 015, the triangles representing them would be in the upper right quadrant of the radar circle, close to the zero.