Sandra Bullock, Louis Bardo and Chelsea Handler Celebrate Charlize Theron's Son Jackson's Birthday

USMagazine, Monday, February 18, 2013, 8:00am (PST)

Charlize Theron invited her A-list pals to help celebrate her son Jackson's first birthday party at her home in L.A. Sunday, Feb. 17. This is the second soiree the Young Adult actress, 37, has thrown for her son, whom she adopted in March 2012.

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Sandra Bullock and her 2-year-old son, Louis Bardo, "arrived with a big bag of presents" from Landis Labyrinth Toy Shop, a source tells Us Weekly. "They stopped to talk to Chelsea Handler as they walked in and Louis showed her a little yellow truck that he was excited to play with."

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(Theron, who has been single since splitting with partner Stuart Townsend in 2010, befriended 37-year-old Handler after appearing on her E! talk show, Chelsea Lately, in December 2011.)

Like Jackson's superhero-themed party at The Coop Jan. 8, Sunday's event "was a low-key, mellow birthday party with only a few close friends and family," the source says. "The kids were running around the yard while the adults sat and chatted. Jackson was practicing walking the whole time and was very happy and active."

The source adds, "At the end of the party there was a birthday cake and everyone sang to Jackson. Sandra and Louis left after about two hours."

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Theron's other famous pals, Marley Shelton and Jason Bateman, attended Jackson's first birthday party in January. The fete featured big lollipops and jelly rings, cupcakes topped with Spiderman's face, and special appearances by Wonder Woman and Batman. "Charlize is the nicest person on earth," an insider told Us of the hands-on mom. "She's gorgeous and relaxed and sweet."

This article originally appeared on Usmagazine.com: Sandra Bullock, Louis Bardo and Chelsea Handler Celebrate Charlize Theron's Son Jackson's Birthday