Brad Pitt's mysterious gift for Jennifer Aniston on her 50th birthday; the actor didn't arrive emptyy-handed after all

Brad Pitt may not have arrived at Jennifer Aniston's birthday party empty-handed after all. Apparently, he had already mailed a gift to Jennifer's home, according to a new report! Get the details!

Reportedly Pitt attended Aniston's star-studded birthday bash at Sunset Tower Hotel in Beverly Hills on February 9. "Most birthday party guests sent gifts to Jen's house. Brad did too," a source tells People! "Her friends are all very generous and creative, and she seemed very excited by all the gifts."

However, what Brad Pitt gifted Jennifer Aniston still remains a mystery. But we can say, that it would have been something special.

Apparently, all of Aniston's friends were reportedly very pleased to see that her ex attended the party. "Her friends were happy to see Brad at the party. Whatever caused their divorce is long in the past," the insider says, adding that Pitt and Aniston — who were married from 2000-2005 — "have a very civil relationship."

A separate source went on to defend the actor, adding, "He was invited, so why shouldn't he go?" — "He's single and has no one to answer to. He and Jen spent many important and happy years together. He obviously decided to join her celebration because he wanted to."

Reportedly other stars in attendance at Aniston's 50th birthday party included: Katy Perry, Ellen DeGeneres, Reese Witherspoon, Robert Downey Jr., Jason Bateman, George Clooney, Orlando Bloom and Pitt's ex-fiancee, Gwyneth Paltrow.

"Friends were a bit surprised, but not shocked to see Brad there, but Jen has been open and honest in the fact that they have spoken here and there since Jen's breakup with Justin [Theroux, 47]," a source told HollywoodLife. "They're friendly and they're on fine terms which is why nobody was totally shocked, but they knew the press and everyone would talk about it. They're not necessarily close, but more friendly."