Lucy Lawless and Renee O’Connor appeared in Hercules long before Xena arrived on the scene. The following are guest appearances in the world of Hercules where they played other characters. See here for episodes where they played Gabrielle and Xena.
Hercules and The Amazon Women:
Telemovie
Guest Starring: Lucy Lawless as Lysia
Hercules meets the Amazon Queen Hippolyta and learns more about the Amazons.

Lucy plays an Amazon enforcer in the first of the Hercules made for telly movies.
Hercules and the Lost Kingdom:
Telemovie
Guest Starring: Renee O’Connor as Deianeira
Hercules and Deianeira go in search of the ‘lost city of Troy’

Renee is fresh-faced and very young looking in this movie. She plays a feisty woman whose secret destiny outstrips that of Hercules himself.
As Darkness Falls
Season One Episode 6
Guest Starring: Lucy Lawless as Lyla
While Hercules is at a friend’s wedding a centaur, Nemis arrives and kidnaps the bride and her maid of honour.
Lucy plays Lyla a centaurs girlfriend who blinds Hercules.
The Outcast
Season Two Episode 5
Guest Starring: Lucy Lawless as Lyla
Hercules is the intermediary between a vengeful centaur and the centaur-hating Cretans who killed his wife.
Lucy reprises her role as Lyla but this time she is in need of Hercules’ help.
For Those Of You Just Joining Us
Season Five Episode 9
Guest Starring: Renee O’Connor as Sunny Day, camp counsellor and Hudson Leick as Liz Friedman, producer
Set in the modern-day, the creators and producers of Hercules: The Legendary Journey go on a camp for inspiration.
Hope against hope that..maybe, Renee and Lucy might do a cameo in the re-boot.
It would be the decent thing to do. And hopefully the producers will make this happen especially if they want fans to support the new show.