Scarlett Johansson's Girls' Night Out
05/22/2012 AT 06:00 AM EDT
The Avengers star and a group of girlfriends popped into Cleo at the Redbury hotel in Hollywood on Saturday night.
Arriving at 9 p.m. and leaving at 11, Johansson wore thick-rimmed glasses and a '50s vintage dressed-down ensemble.
Her table was filled with "lots of laughing," an onlooker tells PEOPLE. "The server was beaming about how sweet she was."
– Jennifer Garcia