AKM-GSITalk about your star-studded parties.
Then again, this is George Clooney we're talking about here, who, along with fiancée Amal Alamuddin, celebrated their engagement with several famous friends at Cafe Habana in Malibu, Calif., on Sunday.
U2 frontman Bono, the restaurant's owner Rande Gerber and his supermodel wife, Cindy Crawford, were among those in attendance.
A source told E! News the low-key celebration was well underway around 7 p.m., noting that the restaurant was very busy because of the Mother's Day crowd.
"People got a show they didn't expect and other [restaurant patrons] said it was the best Mother's Day ever," one eyewitness exclusively shared with E! News.
According to our source, security was on hand as the group partied outside in the back of the restaurant under a covered patio, where there was a lot of hugging and kissing as Alamuddin went around showing off her engagement ring from Clooney.
During the party, the group toasted the engaged duo with shots of tequila, said the source, and there was even karaoke.
Bono actually got up and sang, as did Crawford, who belted out a tune with her daughter.
The source said Clooney looked very relaxed and was constantly smiling and laughing, adding that he and Alamuddin definitely appeared happy and in love.
It was announced in April that the Oscar winner had proposed to Alamuddin after seven months of dating.
This will be the second trip down the aisle for Clooney, who was married to Talia Balsam from 1989 to 1993
—Reporting by Michelle Falls and Senta Scarborough