The actors from the West End musical appeared on the ITV daytime show on Friday, with Amara Okereke leading the cast as Eliza Doolittle.
Alison became emotional as she and co-host Dermot O’Leary spoke to Amara after singing Wouldn’t It Be Loverly from the production.
“I’m so emotional,” Alison said. “I can’t believe how emotional I am just watching that.
“Seeing a Black woman in that role, which I’ve watched since I was a child… I never thought I would ever see anything like that. It’s such a gift, you don’t realise.”
“Doing that role, the representation, what it means to people like me, honestly it’s wonderful,” Alison told Amara. “Such a beautiful performance.”
As Alison wiped away tears and handed over to Dermot, Amara spoke of what it was like to land the role.
She said: “It’s amazing. I can’t lie, it’s intimidating to follow in the footsteps of so many iconic women that have played the role.
“I feel honoured to even have my name in the same sentence as Julie Andrews to be honest.”
My Fair Lady is currently playing at London’s Coliseum Theatre until late August.
The play began on Broadway in 1956, with Julie Andrews among the original cast.
Audrey Hepburn also took on the role of Eliza Doolittle in the 1964 big screen adaptation.
This Morning airs weekdays at 10am on ITV.