It wasn't very surprising to me when Lucky Star's Motteke! Sailor Fuku hit it big on Japan's music charts-- it was immensely catchy and had a little dance to go with it and everything.
I definitely didn't foresee the OP and ED theme for K-On! following in Lucky Star's footsteps, however. I mean, sure, the OP and ED were good...but I didn't remember them being all that amazing, or as I like to say, it didn't really stick with me all that much.
The ending song “Don't Say 'LAZY'” hit the #3 spot on the singles chart,while OP song “Cagayake! GIRLS” took #4. Both songs are sung by the series' four main characters' seiyuu-- that would be Aki Toyosaki (Minami-ke's Yoshino, Shugo Chara!'s Suu) as Yui Hirasawa, Minako Kotobuki (Hatsukoi Limited's Rika) as Tsumugi Kotobuki, Satomi Satou (Jigoku Shoujo's Yuzuki) as Ritsu Tainaka, and Youko Hikasa (Sketchbook ~full color'S~' Minamo) as Mio Akiyama.
For the record, Motteke! Sailor Fuku peaked at #2.
Here are clips of the OP and ED for your perusal. What do you think-- chart-toppers or no?