Argo is an integral part of the tv show, Xena:Warrior Princess. Since Xena's first appearance on Hercules:the Legendary Journeys, Xena has always been associated with horses- possibly making use of Lucy Lawless' horse riding skills.
In those early Hercules episodes she rode a different, sort of dappled colour horse. However, in the very first episode of her own show, Xena and Argo are an item, although the first episode features a male horse and Xena definitely refferring to Argo as 'boy'.
Argo's training was first seen in episode 5, The Path Not Taken, where a whistle from Xena has Argo giving a snarling baddie a swift double hoofed kick. Although Argo's biggest and most heroic role was probably in The Greater Good, where she is Gabrielle's sparring partner, saviour or Xena when she first gets ill, Gabrielle's saviour after she is captured by Talmadeus, and once again, saviour of Xena when she and that other horse refuse to assist in desecrating Xena's body. Another significant episode for Argo was Intimate Stranger, where the body swap between Xena and Callisto results in a life threatening injury for Argo. We also get our first Argo-eyed-view in this episode.
Lucy Lawless' accident during the filming of series two meant there were a number of Argo-less episodes at the end of that series. Lucy was nervous about getting on a horse again, although by the third season Argo is once again a regular.
Argo died in series three's Been There, Done That, but then so has just about everyone on the show! She missed out on the event in Brittania - I guess our quarantine laws got her! However, special mention was made about a different horse being used to drag Gabrielle along at the start of The Bitter Suite by series writer Steven L Sears. He admitted that Argo would not have done that to Gabrielle and Xena had to use a different horse. That episode was also significant in that we saw Xena whipping Argo! A sure sign she was very very angry!
Argo probably looked at her prettiest in the episodeOne Against an Army, in that touching scene where Xena releases Argo, thinking she will die. A few numbers were clearly visable on Argo's shoulder in this scene-(you can also see the numbers in the final scene of the episodeIntimate Stranger.) Argo gets to rear and prance and show off. I wonder how long it took Xena to catch her again after this?
One reason Renee O'Connor as Gabrielle does not have a horse- aside from the fact that only the hero gets a horse- is that it takes THREE horses to play Argo- Tilly, Barbara and Mac, 2 mares and a stallion.
Early reports had the name Daisy assigned to Argo- this is the name of Lucy Lawless' daughter!
Watching the episodes, Argo's whinny is a common feature, and Argo really is a significant character in many episodes.