Gemma Whelan completely transformed herself to play the role of the despised mother Karen Matthews who falsely reported her daughter Shannon Matthews missing.
After pleading on TV for the safe return of her child and 24 days of endless searching, it was later revealed that the mother had orchestrated the plot to bag herself the reward money.
Shannon was found drugged inside the base of a double bed in Dewsbury, West Yorkshire.
And in the two-parter, fans praised Gemma, 35, for her acting talents of portraying Karen and some couldn’t even tell them apart.
Viewers were shocked with Gemma Wheelan's transformation
Moorside: The real story
Tue, February 7, 2017
Moorside: The new BBC drama follows Sheridan Smith, as Julie Bushby, in the search for missing school girl Shannon Matthews. Here's the real story behind the programme.
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One user wrote on Twitter It's actually scary how much @WhelanGemma looks like Karen Matthews! #TheMoorside.”
#TheMoorside, crikey, spot on casting. Gemma Whelan as Karen Matthews looks more like Karen Matthews than Karen Matthews.” Said another.
A third agreed: “I was convinced @WhelanGemma was the actual #KarenMatthews."
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But even more surprising was who Gemma plays in the epic fantasy Game of Thrones.
She has starred as the recurring character Yara Greyjoy since the second season and is an iron born, Theon Greyjoy’s oder sister and his only surviving sibling.
Yara is currently a claimant to the throne of the Kingdon of the Iron Islands and became an ally of Deanerys Targaryen.
Gemma plays Yara Greyjoy in Game of Thrones
Gemma stars as Theon Greyjoy's older sister Yara in Game of Thrones
Viewers have called the actress a "chameleon" for being able to play different roles
And viewers couldn’t believe it.
“OMG just realised that Karen Matthews is Yara Greyjoy Astonishing transformation and performance by @WhelanGemma #TheMoorside.” A shocked Twitter user wrote.
Another said: “@WhelanGemma I think I was more shocked to find out it was you as Karen Matthews than I was when Theon had his 'little accident'! So good.”
“@WhelanGemma And most people don't recognise her from GoT either. True chameleon.” One person added.
The Moorside continues next Tuesday at 9pm on BBC One.