Comedian Jeff Dye shared photos from the fête, which was held on the Warner Bros. lot in Los Angeles, and he did what any of us would do when meeting Beyoncé -- he fanboyed.
"I met Beyoncé tonight and she couldn't have been more sweet," he wrote on Instagram. "And shares my love of costumes."
Beyoncé clearly does love her costumes, as she went all out, sporting a bleached wig, dark eyeshadow and icy blue contact lenses for her role as Storm.
Ciara rang in the big 3-0 at midnight alongside her boyfriend, Seattle Seahawks quarterback Russell Wilson, Beyoncé, and a number of other friends. The daring duo even matched in the perfect couple's costume for the evening: Catwoman and Batman.
A source tells ET that only about 60 people were at the party, including Kelly Rowland and Serena Williams.
Washington native Dye, who was dressed up like Punisher, said the shindig was the “best costume party I’ve ever been [to].”
As for the "I Bet" singer, she got gussied up for her party early. Ciara shared a pensive snap to Instagram earlier on Saturday that showed off the ruby red lips she would be sporting throughout the night.