Robert Downey Jr.'s Lavish Party for Wife's Birthday

Robert Downey Jr. proved he knows how to throw a good party on his wife Susan's 40th birthday this week.

The star-studded weekend-long celebration began Saturday at Cavallo Point Lodge in Sausalito, Calif., near the San Francisco Bay Area, with a birthday party in the hotel's ballroom.

Attendees included Justin Theroux, Jason Bateman, Joel Siler, Gwyneth Paltrow and Reese Witherspoon, among dozens of other celebrities, according to an insider at Us Weekly.

With d├ęcor including purple lights and white roses, the night saw dinner, dancing, and even a photo booth before guests enjoyed a fireworks display at the end of the night.

However, the celebration continued into the next day with a brunch held outside with food trucks from Hapa SF and Bacon Bacon. The menu included breakfast tacos, breakfast sandwiches, omelets and pancakes, as well as a cake made out of maple bacon, chocolate bacon, bacon bits, bacon jam, and vanilla cake, according to the magazine.

Furthermore, throughout the celebration, guests each recorded a message for Susan on her birthday with a videographer.

"Gwyneth Paltrow talked on camera and was laughing and animated as she recorded her message," the onlooker told the magazine.

In the last moments of the birthday party, everyone gathered together to sing "Happy Birthday" to Susan before heading to their next destination.

Meanwhile, the "Iron Man" star and his wife have been married for eight years and share one son, Exton, together.

Downey Jr., 48, is an Oscar-nominated, Golden Globe Award-winning actor who has overcome addiction in recent years. Last year, he was named on Forbes list of Hollywood's highest-paid actors. Downey has appeared in films that include "The Singing Detective," "Tropic Thunder," "Avengers," and "Sherlock Holmes," among many others.