Timmy's Love Song was sung by Timmy Turner in the episode "Oh, Brother". He was trying to sing the song to Tootie from outside of her bedroom window in an attempt to win her heart back, but only Vicky was around to hear it. Although it was sung horribly off-key, Vicky loved it.
Timmy: And so Tootie, can't you see...?
That's why you should love............MEEE!!!
Vicky: I do! I do, mystery singer!!