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Jack Nicholson — Los Angeles Lakers
Arguably the greatest Lakers fan ever, Jack has had courtside seats for more than three decades and rarely misses a game. His trash-talk and scolding of refs and opposing coaches are legendary, and directors reportedly accommodate his shooting schedule around home games. "He's a real fan," former Lakers coach Pat Riley has said. "He's not one of these actors that all of a sudden get front row seats and then they're gone. He's for real. He cares."
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Leonardo DiCaprio — Los Angeles Lakers
It's only fitting that the Los Angeles native and Basketball Diaries star is a Lakers die-hard. DiCaprio tries to stay incognito by wearing a cap when he attends games, but really, can anyone miss that face?
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Spike Lee — New York Knicks
The Knicks super-fan is also one of the loudest, but he temporarily rooted for the Boston Celtics over the Cleveland Cavaliers in last year's Eastern Conference finals in hopes of landing LeBron James for the long-suffering Knicks.
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Eva Longoria — San Antonio Spurs
Longoria's association with the Spurs is bittersweet now that her marriage to point guard Tony Parker is kaput. But as a Texas native, we're sure she still roots for the home team.
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Jay-Z and Beyonce — New Jersey Nets
The couple is notoriously private, but they're very public with their support of the Nets, of which Jay-Z is a part-owner. The rapper has long wanted to relocate the team to his native Brooklyn, N.Y., which should happen in 2012 once an arena is completed
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Ashley Judd — University of Kentucky Wildcats
Ever the proud alum, Judd, who holds a bachelor's degree in French from the school, frequently attends her alma mater's basketball games — and sits in the student section. That's not to say she doesn't support the school's other sports teams: Judd's attended football games and posed for a photo shoot in only a UK hockey jersey as part of a fundraiser.
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Khloe Kardashian — Los Angeles Lakers
The reality star has been a fixture in the crowd since marrying Lamar Odom in 2009. "Watching them play has added an entirely new element of excitement and fun (AND STRESS!) to my life and I have absolutely loved every minute of being their sideline cheerleader!" Kardashian blogged.
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Matthew McConaughey — University of Texas Longhorns
Hook 'em, horns! McConaughey is a mainstay at his alma mater's football games — one of the few times you can catch him with his shirt (a Longhorn one, of course) on. And he's already training his little one to proudly don the burnt orange and white.
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Stephen King — Boston Red Sox
King hardly ever misses a game and frequently sprinkles in mentions of the team in his novels and stories. He also co-wrote the book Faithful: Two Diehard Boston Red Sox Fans Chronicle the Historic 2004 Season with Stewart O'Nan, recounting the team's improbable World Series victory — and the end of the 86-year curse.
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James Gandolfini — New York Jets
The actor can often be seen cheering on the green and white, and it appears the guys are fans of him as well: Former Jets coach Eric Mangini once made a cameo on The Sopranos.
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Jerry Seinfeld — New York Mets
Anyone who's ever watched Seinfeld knows the comedian is a die-hard Mets fan, so know not to offend them in his presence. Last June, Seinfeld called out Lady Gaga, who Mets management sat in his box seats, for giving fans the middle finger during a game. The Mets later apologized to him.
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Billy Crystal — New York Yankees
The comedian and Yankees fan lived out a lifelong dream in 2008 when he signed a minor league contract for a single day to play with the team and was eventually struck out on six pitches. Ironically, Crystal is a part-owner of the Arizona Diamondbacks, who beat his boys during the 2001 World Series.
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Harry Connick Jr. — New Orleans Saints
The New Orleans native is a staple at Saints games and beamed with pride after the team won the Super Bowl in 2010. "It's the greatest time in the history of our city, at least as long as I've been alive," he said then.
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Matt Damon and Ben Affleck — Boston Red Sox
Besides Stephen King, the Bostonian besties are probably the best-known Red Sox fans. Damon narrated the commemorative DVD release of the team's 2007 World Series win and Affleck held the world premiere of The Town at Fenway Park, which itself was featured as the final heist in the action flick.