Alexandra Mardell has revealed working with Simon Gregson is a huge challenge - because he makes her laugh during emotional scenes.
She also told how the pair call each other "daughter" and "dad" after their Coronation Street characters found out they were related.
The 44-year-old actor has taken to jokingly addressing the 26-year-old star as one of his own brood when they are off-screen, after her character Emma Brooker is set to find out Steve McDonald is her real father.
Of the shock DNA plot, Alexandra told Inside Soap magazine: "When Simon found out, he walked up to me and said, 'Hello daughter!'
"Now we just walk around saying, 'Hey, daughter', 'Hey dad'."
While the pair have been tasked with shooting some emotional scenes for the plot, Alexandra admitted it is harder trying not to fall about laughing at Simon - and that can be a real problem.
Simon is so funny that my biggest challenge is trying not to laugh at him.
She said: "Some of the scenes we've filmed together have been so emotional, but Simon is so funny that my biggest challenge is trying not to laugh at him."
Steve was in a relationship with Emma's mum Fiona Middleton - played by Angela Griffin - but she hasn't been in the show since 1998.
Viewers saw Emma make an emotional video call to her mother, who she doesn't have a good relationship with, as Angela made her return as Fiona.
On working with Angela, Alexandra admitted: "I do feel a bit nervous but Angela and I have been messaging, which is nice."
Alexandra was just five years old when her on-screen mum and dad were a couple, but the actress admits it is great that her character has followed in her mum's footsteps.
Fiona worked in the salon and lived in the flat above - both of which Emma is doing now.
Emma discovered the man she thought was her dad wasn't actually biologically related to her in during Monday's episodes (August 12).
She went to visit her 'father' in hospital after he was diagnosed with stomach cancer and he passed away shortly afterwards.
Before he died, he told Emma that he had always loved her like she was his own.
Although Audrey had suspected he was confused with his medication, Emma rang her mum needing to know what he meant.
Emma's mum, who was later revealed to be Fiona Middleton, said that Emma's dad wasn't her biological father.
The shock news, as well as her father's death, left the hairdresser heartbroken.
Viewers praised Ali for her "outstanding" performance.
Coronation Street airs on Mondays, Wednesdays and Fridays at 7.30pm and 8.30pm on ITV.
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