Hold on to your hat

Serena Williams almost ruined a designer pink hat after her Australian Open quarterfinal victory over Johanna Konta in Melbourne on Wednesday.

Williams was signing autographs following the win when she was handed the hat and was about to scrawl on it with marker pen before realizing it was a gift from Aussie race-horse trainer Gai Waterhouse.

"I started to sign it, but I stopped just in time. I have a nice, beautiful hat today. I'm really excited about it," Williams said.

All downhill from here

Roger Federer's four children have been enjoying his Aussie Open run, but one of them is now ready to go home.

The Swiss, who travels with his family on tour, said his kids had been saying: "Don't lose, daddy, we want to stay longer."

But one of his seven-year-old twins changed her mind on the day of his quarterfinal win over Mischa Zverev.

"One of my daughters said, 'It's OK, I want to go skiing in Switzerland,'" he revealed. "I said, 'Come on, give me one more match!"

Karaoke cringe

Grigor Dimitrov got a nasty shock when Roger Federer tweeted an embarrassing video of both of them singing Chicago's 1980s ballad 'Hard To Say I'm Sorry' along with Tommy Haas.

"I was laying in bed watching TV and all of a sudden I got that notification Roger Federer has just posted," Dimitrov said.

"And I was like, 'Oh no, please don't tell me it's this'. And I was like, 'Oh great, thanks man'." Dimitrov could get his own back if he meets Federer in Sunday's final.