Olivia Wilde Pranks Colton Underwood, Wears Wedding Dress to his Nuptials

"Don't Worry Darling" director and Harry Styles' former girlfriend Olivia Wilde broke the rules and wore a white wedding gown to Colton Underwood's marriage ceremony – but she says it was all in good fun, People Magazine reported.

"For the romantic ceremony at the Carneros Resort and Spa in Napa Valley, California, Wilde came wearing a simple silk white dress – in the name of cracking a joke for the newly married couple," the magazine detailed.

"Wilde posted a picture of herself in the dress and a pair of sunglasses holding a matching white parasol to her Instagram Story with the on-screen text, 'Wore a wedding dress to a wedding just so I could make a joke about it in my toast' before adding another photo of her hugging Underwood, 30, with Brown, 39, standing near and text reading, 'The grooms approved,'" the article went on to add.

Not everyone was a fan of the joke, however.

"Firstly, who knew they were friends and secondly... why is she wearing a wedding dress?" news.com.au huffed.

"The whole thing feels like a plot stolen from Ryan Murphy's 'Glee,'" the news outlet added, before questioning whether Underwood and his groom, Jordan C. Brown, "may have only found out about her wedding dress gag at their wedding? Honestly, the plot thickens."

Online reaction was decidedly mixed, the newspaper noted.

"Olivia Wilde showing up to her friend's wedding in a white silk wedding gown is ... desperate," the account quoted one person as posting, while others called Wilde "narcissistic" and said she had "gone wrong."

As previously reported, the grooms opted for natty attire in their own right; People Magazine reported that Underwood and Brown went to the altar with "custom Tom Ford suits."

"Underwood went with a deep green, while his political strategist husband chose blue, both as a nod to the natural setting of their 'I do's,'" the magazine detailed.

Have a look at some of Twitter's reactions to Wilde's wild fashion statement.