Celebrity Showdowns: Which World Series teams are these rival stars rooting for?

Stars: they're just like us. Meaning, in this case, that they have really, really strong opinions about sports. Here are some celebrity friends (and foes) who'll find themselves on opposite sides of the 2013 World Series. Who ya got?

John Slattery (Red Sox) vs. Jon Hamm (Cardinals)

Mad Men's real-life Roger Sterling and Don Draper fiercely support the teams of their respective birthplaces, though they'd no doubt love to take on either franchise as a client.

Lil Wayne (Red Sox) vs. Nelly (Cardinals)

Lil Wayne, who's blogged about sports (he also loves the Lakers and the Packers) for ESPN.com, dropped a reference to his Boston cap in "I'm Good." His friend and collaborator Nelly threw a ceremonial first pitch at Busch Stadium in August.

Jimmy Fallon (Red Sox) vs. Andy Cohen (Cardinals)

These late-night hosts take baseball seriously, people. Andy Cohen adopted a dog and named it Wacha. Jimmy Fallon starred in a movie about being a Red Sox fan.

John Krasinski (Red Sox) vs. Jenna Fischer (Cardinals)

Jim and Pam may be a match made in heaven, but Office co-stars Jenna Fischer (raised in St. Louis) and John Krasinski (a native of Newton, Mass.) have very different loyalties when it comes to baseball.

... plus Ellie Kemper and Phyllis Smith (Cardinals)

Looks like John/Jim is alone on this one. Ellie Kemper -- also known as Erin, Dunder Mifflin Scranton's receptionist -- and Phyllis Smith -- who played, duh, Phyllis -- are both from Missouri, and both love the Cards. In fact, Kemper was once a student in Jon Hamm's high school drama class.

Keegan Bradley (Red Sox) vs. Rickie Fowler (Cardinals)

The PGA rivals will have plenty of time for trash talk on the links. Rickie Fowler -- who takes in plenty of St. Louis spring training action near his home in Jupiter, Fla. -- recently attended NLCS Game 4. Superfan Keegan Bradley considers Boston's 2004 World Series win one of the happiest moments of his life.

Kenny Chesney (Red Sox) vs. Gretchen Wilson (Cardinals)

Kenny Chesney, a lifelong Boston fan, once told People he'd "love to play second base" for the team. Fellow country star Gretchen Wilson actually recorded a song in honor of her beloved Cards, "Redbird Fever."