Now you’re in for some serious butt-wagging! 
If I recall correctly this song was written by the same people that wrote Lupin.
You might remember that I generally don’t like the use of the word “Mr.” in song titles, but here it is the title, so it’s OK. 
The DVD didn’t say when this was recorded and I couldn’t find the performance on YouTube, but then I came across another performance from the same show (same stage). It turns out that it’s the same show where Yu-ri from SNSD performed Get Right.
2010-08-03 (Tue) 01:23
And Yuri’s litle cowboy belt buckle dance in that was realy cool. Gota love Yuri. Kara are looking amazing once again here.
2010-08-03 (Tue) 15:53
lol, but wagiging intro makes this proformance an insta win
2010-08-03 (Tue) 20:11
I read somewhere that the dance number was what made this song more popular than Wanna from the same album and the reason why it’s KARA’s first single in Japan.