Other mistake: In Season 2 "Ten Little Warlords," Ares tells Xena that without a sitting God of War, peaceful people can't control their anger. Yet during the whole time in Season 6 that Ares is mortal, peaceful people can control their anger. Furthermore, in Season 6, Ares tells Xena that without the God of War the Goddess of Love becomes unbalanced. Yet in Season 2 there is no mention of this.
Xena: Warrior Princess (1995)
1 other mistake in season 6
Beware Greeks Bearing Gifts - S1-E12
Revealing mistake: At the end when Xena is fighting Deiphobus, he pushes her up against a large rock, every time she hits the rock it moves, as if it were foam.
Trivia: Karl Urban, who plays Cupid in this episode, also plays Caesar in many episodes.