Luckily, plenty of attendees did fit that bill, and while it's no surprise that big stars have other big star friends, some of the guests at the Ojai reception didn't strike us as being the most obvious of besties with the southern belle.
So what was their connection? Let's break it down…
Gwyneth Paltrow: Other than being pretty blonde Oscar winners with two kids and penchants for singing, who knew these two had anything in common? Turns out, they've been hanging out for years, and even spent Thanksgiving of 2008 together in London—with one other very special (at the time, anyway) guest: Reese's then-beau Jake Gyllenhaal, who in all likelihood is responsible for forging the friendship between the two pals. Jake and Gwyneth go way back (she even sheepishly admitted to setting up him and Taylor Swift a few months back) and costarred together in 2005's Proof.
Renee Zellweger: A longtime pal of Reese, the blonde, Oscar'd duo (hey, we're sensing a pattern in her friend selection technique here) share the same social circle and have many common friends. Though not enough to keep Renee around for the actual reception.
Scarlett Johansson & Sean Penn: The real question here isn't what Scarlett was doing at the wedding (she's a client of Jim's), but what Sean Penn was doing at the wedding. Play coy all you want, you two, but taking someone as your wedding date trumps all the denials in the world.
Tobey Maguire: Tobey and wife Jennifer Maguire could've sat on either side of the aisle, as he's got connections to both the bride and groom. As well as being represented by Jim, Tobey costarred alongside Reese in 1998's Pleasantville.
Robert Downey Jr.: Here's another one with multiple connections. While Robert is repped by new groom Jim, he's also a pal of Reese's and he and his wife Susan frequently socialized (and exercised!) with Reese and then-beau Jake in Ojai.
Matthew McConaughey: Sure, he may be southern and charming and currently costarring alongside Reese's ex Ryan Phillippe in The Lincoln Lawyer, but this star's connection isn't through Reese—McConaughey is repped by Toth.
Alyssa Milano: Surprisingly enough, it might've been Milano who was the plus-one for this event, as her new hubby, agent David Bugliari, works alongside Toth at the Creative Artists Agency. However, Milano also costarred alongside Witherspoon in 1996's Fear.
Colin Hanks: Perhaps he was just responding in kind—Toth and Witherspoon were guests at his wedding to publicist Samantha Bryant last year—but in any case, while friendship has clearly blossomed, the connection here started out professional, as Hanks is also repped by CAA.
Salma Hayek: Didn't know Reese and Salma hung out? Well, they probably will now, since Reese just married her agent.