Charlize Theron Celebrates Son Jackson's 1st Birthday With Superhero Party: All the Details!

USMagazine, Friday, January 25, 2013, 12:00pm (PST)

They grow up so fast! It seems like just yesterday that Charlize Theron brought home baby Jackson, but in fact almost a year has passed since she announced his adoption in March 2012. Earlier this month, the single Snow White and the Huntsman star, 37, celebrated a huge milestone with her son: his first birthday, which she marked with his first birthday party.

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On Tuesday, Jan. 8, Theron hosted a superhero-themed shindig for her little boy at the Coop, a play space for kids in L.A.'s Studio City. (Ashlee Simpson and ex-husband Pete Wentz threw a similar bash at the same venue for son Bronx's 4th birthday in November.) The fete featured big lollipops and jelly rings, cupcakes topped with Spiderman's face, and special appearances by Wonder Woman and Batman. (Plus champagne for the parents!)

"It was a really mellow party," a source tells Us Weekly of the celebration, which was attended BY a few of the actress' famous friends, including Marley Shelton and Jason Bateman, who brought his 11-month-old daughter Maple. "Charlize is the nicest person on earth. She's gorgeous and relaxed and sweet."

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She's also a fantastic mother. "Charlize absolutely adores [Jackson]. They have the most wonderful relationship," the insider gushes to Us. One sweet example of her maternal instincts? "[Jackson] was jet-lagged, so when everybody sang 'Happy Birthday,' they had to whisper it. She didn't want it to be really loud."

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In fact, the Oscar winner has been a doting mom ever since adopting the tot last year. "It's an overwhelming sensation of love," Theron gushed to E! News of motherhood in May. "There's almost a moment where I feel like I can't remember anything prior to him. I feel like it was always just meant to be what it is. Everyday I'm just like, 'It's not possible to love you more,' and then 20 minutes later you're like, 'Oh my god! How is this possible?'"

This article originally appeared on Usmagazine.com: Charlize Theron Celebrates Son Jackson's 1st Birthday With Superhero Party: All the Details!