He walked the red carpet alone.

But Ryan Gosling's sister Mandi, 40, filled in for his girlfriend Eva Mendes at the Academy Awards in Hollywood on Sunday.

According to Daily Mail, social media platform Twitter went wild over the identity of the 36-year-old's date as the ceremony aired on Sunday night.

It's not the first time Gosling has been joined by his glamorous older sister, an LA producer who helped produce Pharrell Williams' Grammy award-winning song Happy.

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Mandi, who Gosling once credited with helping him 'think like a girl', has appeared as her brother's date at numerous events over the past decade.

Mandi, who appears to be single and has also worked as an associate producer on Dateline, has also accompanied Ryan to countless movie premieres and other celeb-packed events over the years.

Ryan Gosling with sister Mandi Gosling and mother Donna Gosling. Photo / Getty
Ryan Gosling with sister Mandi Gosling and mother Donna Gosling. Photo / Getty

She was even at her brother's side for his first Oscar nomination ten years ago.

The event, clearly a proud moment for the star, who turned the event into a family affair, also bringing his mother Donna for his best actor nomination for as a drug-addicted teacher in Half Nelson in 2007.

Although he didn't win, that did not stop him inviting his sister along when he was nominated for a Screen Actors Guild Award for Lars and the Real Girl the following year.

Mandi Gosling, Ryan Gosling and Donna Gosling. Photo / Getty
Mandi Gosling, Ryan Gosling and Donna Gosling. Photo / Getty

The brother and sister sat together snacking on the free sweets that fell from the ceiling during the ceremony.

But never has she caught the limelight as much as she did at this year's Oscars in her low cut gold ensemble.

Her social media pages reveal it's not the first outing for that knockout dress. She also wore the golden stunner at her 40th birthday celebrations last month.

Comments online primarily centered in on Mandi's cleavage.

Singer Justin Timberlake, Mandi Gosling and actor Ryan Gosling attends the 89th Annual Academy Awards. Photo / Getty
Singer Justin Timberlake, Mandi Gosling and actor Ryan Gosling attends the 89th Annual Academy Awards. Photo / Getty

User MaryWallYall said: 'Just found out the boobs by Gosling is his sister and now I feel a little awkward.'

Another from user Ginny asked: 'Who belongs to the boobs next to Ryan Gosling?' 'Who is boobs mcgee that's with ryan gosling?', added Babe Ruthless.

Some Twitter users even correctly theorized the woman beside Ryan was his sister.
Twitter user Vito Selvaggi hilariously tweeted, 'Someone introduce me to Ryan Gosling's sister.'

'Have we figured out who @RyanGosling's date is? His sister?? She's gorgeous,' wrote Melissa Kenney.