Margot Robbie and Kylie Minogue show support for marriage equality in Australia

For all the jokes, laughs and lunacy Margot Robbie brought to Saturday Night Live's season 42 premiere last night, there was at least one serious moment.

But it was subtle.

If you weren't paying attention when Robbie introduced The Weeknd's second musical performance of the night, you might have missed the details of her black t-shirt.

Robbie's shirt read “Say ‘I Do’ Down Under,” along with a map of Australia in rainbow colors.

Though Robbie (an Australian herself) didn't directly address her shirt during the show, the phrase is part of an Australian same-sex marriage advocacy campaign from British actor Joshua Sasse, who is Kylie Minogue's fiancé.

"I was shocked to find out earlier this year that same-sex marriage in Australia is still illegal," Sasse writes on the campaign's website. "There are many hurdles to jump in order to make constitutional change, but we are now the closest we’ve ever been to that change."

Sasse revealed on Thursday that the couple will be holding off their wedding until marriage equality is legal in Australia.

"Why are we any more important than anyone else? It's not right, and something has got to be done about it," he told Sunrise.

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The campaign is brand new (its Twitter and Instagram posts only go back one day) and will surely see a boost in popularity from Robbie's support. Kelly Ripa and Dolly Parton have also been associated with the campaign in the past day.

UPDATE: Oct. 6, 2016, 1:59 p.m. AEDT Updated with comments from Joshua Sasse.