Celebrities had children on the brain in 2008. Baby bumps were everywhere, and Hollywood is starting to resemble a playpen.

There were plenty of stars who didn't shock us too much when we found out they were in the family way. Christina Aguilera and hubby Jordan Bratman had baby Max. Jennifer Lopez and Marc Anthony had twins they named after the kids on "Dragon Tales." Gwen Stefani and Gavin Rossdale welcomed Zuma Nesta Rock. It wasn't even that surprising when Jessica Alba announced she was going to have a baby with her longtime beau, Cash Warren. And we didn't fall off our seats when Nicole Kidman and Keith Urban welcomed Sunday into the world. There are plenty of famous couples who are still perpetually rumored to be pregnant: Avril Lavigne and Deryck Whibley, Mariah Carey and Nick Cannon, and Jen Aniston and John Mayer. (There were also some parents who went from famous to notorious this year.)

And then there were the celebs that made us stop dead in our tracks when we found out they'd be having a kid (or two). Here are the most surprising parents of 2008:

5. Brad Pitt and Angelina Jolie
OK, they love kids, but you'd think that after four, they'd want to slow down a bit. But these two can't stop adding to their brood. To be honest, they are beautiful and rich, so it's sort of like why not? So, with that in mind, this year they went from four babies to six when in July, Knox Leon and Vivienne Marcheline, came into the world.

4. Nicole Richie and Benji Madden
It's always sort of surprising when two free-spirited, wild people get together and make a baby. This was the case when Nicole and Benji gave birth to little Harlow Winter in January. They've each been out there and sowed their wild oats, and now they're changing diapers!

3. Ashlee Simpson and Pete Wentz
Ashlee sort of denied her pregnancy in a way that made everyone suspect it even more. Then Pete got defensive about it. And then, finally, Pete confirmed the whole thing on his blog. Actually, after their quick engagement and wedding in May, the fact that these kids were having a kid was less surprising than the name they chose for their bundle of joy, Bronx Mowgli.

2. Jamie Lynn Spears and Casey Aldridge
Technically, the littlest Spears shocked the world back in 2007 when she announced her pregnancy. But since the 17-year-old gave birth to daughter Maddie Briann in June of this year, she still counts, right? Opting to raise her baby with boyfriend Casey Aldridge (who's become a tabloid magnet in his own right) near her family's home in Louisiana, the former "Zoey 101" star worked to get her GED and has some plans to go to college in the future.

1. Clay Aiken
Perhaps the Claymates were the only ones surprised to learn the "American Idol" runner-up is gay, but the earlier news that he was going to be a father made quite a ripple. The American Idol and his friend Jaymes Foster decided to raise son Parker together. "I cannot raise a child to lie or to hide things," the singer said when he came out and introduced his son in the same People article. "I wasn't raised that way, and I'm not going to raise a child to do that."

Honorable mentions

Ricky Martin had twins via surrogate. Taylor Hanson, 25, and his wife welcomed their fourth child and named him Viggo Moriah (his brothers both had kids this year too). "Full House" alumna Jodie Sweetin had a kid only months before announcing she was getting divorced. Action star Vin Diesel and his model girlfriend had a daughter when no one was looking. Minnie Driver had a son but refused to name the dad. Alaskan first daughter Bristol Palin announced that she was expecting a bundle of joy, courting some controversy for mom, VP candidate Sarah Palin. Lisa Marie Presley had twins (insisting she wasn't just fat). Usher and his wife had another kid, Naviyd Ely Raymond, only a year after the birth of Usher Raymond V. And, of course, there was the pregnant man ...