Popsinger Jason Derulo dropped by hot new club Amnesia NYC and drove the crowd — including Rachel Hunter and Chris Noth — wild by introducing his hit single, “Whatcha Say,” Thursday night. A spy told us: “He hung in the booth with DJ Vice, and the crowd went crazy when he introduced his song.” He’d better get used to the attention — Derulo is going to be the opening act for Lady Gaga‘s Monster Ball Tour, which he’ll join on Dec. 28, following Semi Precious Weapons and Kid Cudi.