Meet Shortland Street's newest and youngest cast members who play Ali and Lucy's baby

Julia Fitzpatrick and daughter Olivia Tangi, Stefanie Wilson and young Abigail.

New Zealand's most-loved drama Shortland Street has welcomed its newest - and youngest - cast members.

Young nurse Lucy Rickman (played by Grace Palmer) gave birth to her first child to her ambulance driver husband Ali Karim (played by Tane Williams-Accra​) in a car during Thursday's explosive 90 minute episode celebrating the 25th birthday of the show.

Earlier this year casting director Andrea Kelland put out call for pregnant women who had babies due mid-March to audition their newborns for the role.

The Herald on Sunday can now exclusively reveal the identity of the two little ones chosen to play Ali and Lucy's bundle of joy.

Little Olivia Tangi and Abigail Wilson share the part so that the babies and their families are only required on set a few hours a week and aren't overworked.

The pair scored the role after their respective mums, Julia Fitzpatrick and Stefanie Wilson, each found out through social media that the show was recruiting.

The casting call required the baby to be of mixed European and African or Middle Eastern descent.

Fitzpatrick, who has Jamaican and European heritage and whose partner is Tongan, thought her baby would "tick all those boxes", so on March 8, a few days before Olivia's due date, she enquired about the role.

Olivia was born later that day and was 12-days-old when she first when on set.

Her proud mum said she was excited when she found out Olivia had been cast because she was a huge fan of the show and had been watching since it hit Kiwi screens 25 years ago.

"I was actually an extra on Shortland Street years ago - I did a scene in The IV when Shannon and Tama were on - so it was quite funny going back there."

The days when they have filming are very different from an average day when Fitzpatrick's running her Arbonne beauty business, she said

"We're pretty much only on set for about an hour each time. 90 per cent of the time when she's been filmed she's been asleep so far."

After arriving and getting Olivia dressed in the outfit she'll be wearing for the scene Fitzpatrick feeds and settles her.

"Then they'll call us in and do the shots they want. They're really organised so you just kind of go in there and it's quite quick."

Wilson, who is also a Shortland Street fan, said she was surprised when Kelland called to say Abigail, who was born on Valentine's Day, would star on the show.

"I've been a fan of the show for quite a while so it was a bit surreal actually that my daughter's going to be on there.

"It was very unexpected. I just thought I'd give it a go because she was slightly older but she was born earlier than her due date and she was quite little anyway."

Although Abigail doesn't have any African or Middle Eastern heritage, she's the right colouring to play Ali and Lucy's baby, as Wilson is Indian Malaysian and her partner is European.

Abigail's on screen mum Grace Palmer was "absolutely in love" with her and Tane Williams-Accra​, her Shortland Street dad, had also bonded with Abigail.

"It's so much fun for me and she's very, very relaxed. Everyone's so lovely and it's been really good. When we walk in everyone's all over her," Wilson said.

"She literally just gets passed around from one person to the other when we're there, which is quite good, and she's slowly getting to know everyone."