Finally found it!

     Ever since I finished watching You're Beautiful, the Piano scene of Jeremy and Go Mi Nyu in episode 15 has been bugging me non-stop. I knew I heard the melody Jeremy sang before. But I could not recall where I heard it from. Grr!!!

     Fortunately, after half day searching over the internet, I found this site: xitsyou. Thanks to the owner, I finally know from the entry [091126] 미남이시네요 dated November 26, 2009 that the scence was actually a parody of Lee Jun Ki's Pomegranete CF. I also got a bonus and found out that the scene of Kang Shin Woo and Go Mi Nyu was also a parody. The original CF was of Maxim TOP coffee (Won Bin and Min Ah).

Here is the Jeremy and Go Mi Nam scene (parody):

 

Here is the original  Lee Jun Ki Pomegranete CF (with subtitle):

     Unfortunately I could not find any clip of the Kang Shin Woo and Go Mi Nam parody. You'll have to watch the episode see it. But here is the mentioned Maxim TOP CF.

     Enjoy! I know I did. Especially after not remembering where I heard the melody even after trying so hard and humming the melody the whole day. Yeay! (^_^)