Serena Williams curious about Nick Kyrgios fans' 'blackface' tweets

The Aussie fans at Wimbledon have been some of the most raucous spectators in the All-England Club stands. But the last few days, they have also become the most politically incorrect on social media.

Several fans of hot-head Nick Kyrgios have been posting photos of themselves having spread Nutella or Vegemite on their face in support of Kyrgios, who is the brown-skinned son of a Malaysian-born mother.

Some critics have claimed the resulting effect has disturbing racial undertones.

Now Serena Williams is questioning how the bizarre memes of tennis fans “blacking up” their faces in tribute to the Australian bad boy have been allowed to thrive at Wimbledon.

“Oh, gosh. Really? I didn’t know that,” Williams said Monday, when asked about the fad. “I think you’re better asking the fans that question. Maybe they can give you some insight. And let me know, I’d be interested to know.”

Kyrgios tweeted his blessing to fans covering their faces in popular Australian bread spreads.

One fan, Mitchell McConachy, attempted to show his support for his tennis idol by telling Kyrgios he would volunteer to cover his face in Vegemite if the rising star replied to him through his official Facebook page.

Kyrgios was all for it, to say the least. Then it just snowballed.

So this has sort of taken off... fans covering their faces in weird and wonderful stuff, this time delicious... http://t.co/lMeMXz5m6X

— Nicholas Kyrgios (@NickKyrgios) July 5, 2015

Then a small legion of fans followed his example by covering their faces with Nutella. He told another fan she was “awesome” for covering her face in the hazelnut spread.

Kyrgios’ Wimbledon run ended Monday in a fourth-round defeat by Richard Gasquet.