The series, which screens on TVNZ and TVNZ OnDemand stars Lawless as private investigator Alexa Crowe.
O'Connor is set to guest star in an episode as Clarissa Klein, a self-help guru who clashes with Lawless' character as she investigates the death of Clarissa's spouse.
Speaking to Entertainment Weekly, Lawless shared that reuniting with O'Connor onscreen was "always" something they were keen to do.
"Life just didn't work out that way. But I was like, by hook or by crook, now that I'm the boss — one of the bosses [Lawless is an executive producer on the show] — this is happening," said Lawless sad. "Because at this time of your life, there's only love. Only these things matter, caring for one another, doing things that aren't expedient, do the hard thing just because you love."
O'Connor shared she had "some nerves" before filming since it had been a few years since she was last on a set.
But Lawless put her fears to rest and sent her the show tape before it was her time to perform.
"It just felt like walking into Lucy's living room and having friends over. It was so charming and loving," O'Connor said. "And it was like that all the way to the very end. I actually had a little withdrawal when I finished filming."
Lawless described the reunion as being "like a warm bath," as it was "so easy" for them to work together again.
"I suppose because Ren and I also, we've played a lot of different roles with one another. It wasn't like we were stuck in a certain mindset with our relationship to one another as actors," continued Lawless, who also had a joint cameo with O'Connor in 2009's Bitch Slap. "We got to play dual roles and all kinds of things [on Xena]. So, it was just more play."
Lawless is also set reunite with Xena's Bruce Hopkins and Spartacus' Anna Hutchison and Graham Vincent.
