Faux (fake, artificial, not genuine); Excitement (exhilaration, the feeling of lively and cheerful joy).
When a person or a group of people masquerade their true feelings (about something that is meant to be exciting) by showing extreme excitement.
A: OMG! I just got tix to Justin Beiber's show!
B: What?! When?! How?! Wow!!!! That's SO AWESOME!!!!
(Person A, is unfortunately, genuinely excited).
(Person B show's great faux-excitement).
(Person A is a dumbass).