Nicole Richie's daughter has celebrated her fourth birthday with a 'Toy Story'-themed party.

The fashion designer - whose House of Harlow 1960 clothes collection is named after her little one - and husband Joel Madden celebrated Harlow's latest milestone at Studio City, California with a number of celebrity guests.

Nicole and Joel - who are also parents to two-year-old Sparrow - were joined by Bush rocker Gavin Rossdale, who brought along his and Gwen Stefani's children Kingston, five, and three-year-old Zuma.

Tobey Maguire's wife Jen Meyer, Sara Gilbert and Rachel Zoe and their kids also attended the event, which took place at the same venue where Ashlee Simpson and Pete Wentz threw Bronx Mowgli's third birthday.

An onlooker told Us Weekly magazine: "Harlow started crying when everyone sang happy birthday and Joel said she was crying tears of joy."

Harlow's party was attended by 35 kids, who were treated to a visit from the Pixar animation movie's star characters Woody, Buzz Lightyear and Jessie.

An insider added: "Everyone had a blast and Joel and Nicole said it was their best kids party yet."

Harlow and her fellow partygoers indulged on a feast of pizza, juice and sugar-free cake at the bash.

It is not first time Nicole, 30, has been associated with 'Toy Story'.

She dressed up as cowgirl Jessie to celebrate Halloween in 2010.