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Charlize Theron Throws Birthday Party For Son Jackson, Sandra Bullock and Chelsea Handler Attend

by Tierney Bricker and Melanie Bromley Mon., Feb. 18, 2013 7:46 PM PST

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Charlize Theron's son Jackson has only just turned one, but he already has at least two famous friends!

The actress hosted a birthday party for her son at at her Hollywood Hills home on Sunday and Theron's A-list BFFs Sandra Bullock and Chelsea Handler were on hand to help celebrate Jackson's big day.

And we've got exclusive details on what went down inside the bash!

Charlize and Jackson recently enjoyed a play date in West Hollywood

"Sandra Bullock was one of the first guests to arrive with her son Louis," an eyewitness exclusively tells E! News. "As they walked into the party, they bumped into Chelsea Handler who had also just arrived in a limousine. They all walked in together and headed for the backyard where children's music was playing and kids were running around."

Our source says around 20 people attended the birthday bash, which they described as "a low-key party with only close friends and family...There was a lot of laughter and screams as everyone had a good time."

And it seems like Theron and Bullock's little ones are quickly becoming BFFs, too! "Louis and Jackson had a great time running around playing together, but they were both worn out and looked ready for a nap," our source says, adding that Bullock "brought a big bag of presents from Landis' Labyrinth Toy Shop" that she had picked out.

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