Mean Girls fans admit their shock at learning Rachel McAdams played the role of Regina George - as viral TikTok reveals little-known secret about her transformation into high school villain

Multiple Mean Girls fans may find themselves in the Burn Book after admitting that they had no idea Rachel McAdams had played the role of Regina George - the original Mean Girl - because she was wearing a blonde wig in the movie. 

A TikTok user posted the stunned video after realizing a blonde McAdams played the Queen Bee in the 2004 film - and many followers were equally as shocked by the news.

'Rachel McAdams wore a $20,000 wig while playing Regina George in Mean Girls because she didn't want to bleach her hair, and after the film it sold for $600,000.' user @sakuraxea wrote on the 10-second clip.

The video has been viewed over 15.2 million times, with over 3,300 comments from dumbfounded users who didn't know the Queen of North Shore High School was played by the now 45-year-old actress.

'I was today years old when I found out Regina George is Rachel McAdams,' one user declared.

'I always thought Regina and the actress from The Notebook were different,' one amazed follower commented. 

'It was like last week when I found out that Regina was Rachel McAdams not Lindsay Lohan (idk why I always thought that),' agreed another.

'The personality change from Mean Girls to The Notebook. Truly a star,' one chimed in.  

'Omg I NEVER would've thought that was a wig,' a stunned user wrote.

'So they weren't joking when they said that her hair was insured for 10,000 dollars,' another quipped, making reference to the iconic line from the movie.

In reality, McAdams wore the blonde wig because she was filming The Notebook, another 2004 blockbuster, at the same time.

News of the wig came to light in a 2016 interview with Rajiv Surendra, who played the legendary mathlete Kevin Gnapoor in the movie.

When speaking to Seventeen, the actor revealed that McAdam's blonde locks were 'not her hair in the movie.'

'They had a wig made out of human hair by a very well-known wig maker from this little town called Stratford, Ontario,' he explained.

He went on to explain he's not certain if it's true, but he heard the actress didn't want to bleach all her hair.

'So the front bit was bleach blonde, so that was her real hair, but the wig was fake,' he explained.

'I remember walking in to the makeup and hair trailer regularly and seeing the wig being washed. 

'They actually would wash it and put this little shower cap thing on it that they would hook the blow dryer onto that would dry the wig,' he recalled. 'It was like a $10,000 wig.'

The actual cost of the wig is unknown, as is how and where the wig sold.