“Luke stayed close to the bar near the pool and spent the evening chatting up girls,” an onlooker tells PEOPLE. “But he left the party alone around 1 a.m.”
Dancing With the Stars dancers Val and Maks worked the party together, opting for a tour of the infamous grotto.
“They looked kind of fascinated as they exited the grotto,” the source adds.
Barker arrived later, making an entrance around 12:30 a.m. with an entourage of male friends. “He was pretty low-key,” the source says.
As for the evening’s host, Snoop Dogg – who now goes by Snoop Lion – arrived after midnight as well to celebrate his birthday in a VIP tent.
“Laid back wit @JDMetro, @EvanMetropoulos, @HughHefner. Uhearme! @Playboy mansion #WorksEveryTime,” he wrote sharing a photo on Instagram.
– Melody Chiu