Awww....

Don't you just love it when your kids kiss you with the pacifier still in their mouth? I simply melt...

Since we're into riddles...

Please check out the following 2 lines:

1) AEFHIKLMNTV
2) BCDGJOPQRSU

The letters A..V are all present here. The letters W,X,Y,Z are missing. My question is - where do they belong (which line) and why?

Update: solution already in the comments. (Way to go ijon!) Don't look if you wanna exercise your gray matter ;-)