Andy Roddick was cracking crude jokes. Kim Clijsters stunned the crowd by trying a running chest-bump with Sam Stosur. Rafa and Roger took time out from their rivalry to exchange high-fives and play on the same side of the net.
The sold-out fundraiser for Australia's flood victims - dubbed the ''Rally for Relief'' - came on the eve of the Australian Open and raised $1.8 million within hours on Sunday, an amount that organizers said was expected to grow.
In Melbourne, which has escaped the floods, it was blue skies and laughter on center court. Some of the players wore microphones, poking fun at each other and mixing entertainment with pledges of support for the devastation that has been described as one of Australia's worst natural disasters.
''We've all been very shocked and surprised by a lot of the images,'' No. 3-seeded Clijsters, a three-time U.S. Open champion, said before the event. ''If we can help in any small way, I think it's our obligation to be out on that court ... and influence people to donate more money and help the others who aren't as lucky.''
The floods have caused at least 27 deaths in Australia's northeast since late November, and 14 other people are missing, most of them from a flash flood compared with an ''inland Tsunami'' that swept through towns west of Brisbane, Australia's third-biggest city, on Monday.
''Hopefully, we can take some of the stress away,'' Clijsters told the Rod Laver Arena, packed with 15,000 fans.
First up, No. 8-seeded Roddick and No. 5-seeded Andy Murray teamed up with two-time major finalist Vera Zvonareva and Victoria Azarenka in a rotating mixed-doubles game against No. 3-seeded Novak Djokovic, No. 1 Caroline Wozniacki, seven-time Grand Slam winner Justine Henin and Ana Ivanovic.
Djokovic and Roddick whacked balls with exaggerated grunts, mocking some of the female players' sound effects.
When Ivanovic aced Roddick with a slow serve and an exaggerated ''uhhhhhhhh,'' he responded with a raised hand: ''Sorry. I was distracted,'' drawing cheers of laughter. Roddick noted he preferred to stay at the baseline behind his female teammates at net because it was ''a good view.''
Djokovic, who won the 2008 Australian Open and is nicknamed ''The Joker,'' jumped into the photographer's pit at one point and aimed a telephoto lens at the long-legged Wozniacki, in a short tennis dress: ''Hey Caroline, I can see much more than you think.''
In the next round, it was the women's turn to mock the men.
No. 1-ranked Nadal teamed up with No. 2-ranked Federer against Clijsters and Australian favorite Sam Stosur.
The ladies celebrated one winning point with the ultimate in tennis testosterone: the running chest bump made popular by American doubles pair Mike and Bob Bryan, drawing pained cries of ''Ouch!'' from the crowd.
Camaraderie came first Sunday, but the longtime rivals did play a few points against each other in which Federer whipped a backhand winner past Nadal and the Spaniard responded a point later with an airborne smash at net.
Nadal is on a quest to win his fourth consecutive Grand Slam, a feat not achieved since 1969. Federer is defending champion and vying for his fifth Australian Open title and his 17th Grand Slam singles victory.
''It's just nice to help because, I think at the end of the day, it's a dream come true for us to be tennis players,'' Federer told the crowd. ''That's what it's all about, to give a little bit of our time for people who need it much more than we do.''
Last year, Federer organized a similar charity event with Nadal and other stars for victims of the Haiti earthquake.
Nadal added: ''I think it's really nice that the tennis family are together to support these difficult times.''
Seats cost about $20 - a fraction of the normal price for a Grand Slam match - and tickets sold out almost immediately. The event itself raised $1.8 million through ticket sales and donations. Players competing Sunday also planned to donate the shirts they wore in the exhibition in a ''Shirts off their Backs'' auction expected to raise thousands more for the flood appeal.
