I don't know if I need a spoiler for this, but the two-handed heart gesture the girls made during the OP dance is a signature move for
Morning Musume, requently made by two of the "cute" members,
Michishige Sayumi and
Kusumi Koharu. The gesture is also part of Kusumi Koharu's PV dance for "Balalaika", the OP of the extremely popular young girl's anime, "
Kirarin Revolution".
I guess everyone knows that KyoAni OP/ED dances are parodies of
Hello! Project groups, right? I was playing the 2006 Momusu concert as I was building my home gym last night and boy, I would guess that the great majority of the Wotas at the concert probably watched both Haruhi and Lucky Star. There's must be a huge overlap between idoru otaku and anime otaku.