Fat girls like...
Les gusta a las gordas...
The kid used to like me...
Yo le caía bien al niño...
You seem to be a bit confused about the use of verbs such as these, so I'll try and help.
Les gusta a las gordas = Literally means To the fat girls it(something) pleases them...
"les" in this sentence refers to the fat girls and "gusta" refers to whatever it is that pleases them.
Yo le caía bien al niño... I used to fall well to him. (Strange sounding, no?) It really means "He used to like me." Le once again refers to the kid (niño) and caía refers to myself, or yo.
Do you notice the pattern? Things are a bit reversed in cases such as these from English. That's to say, in English we would be the object of the sentence, or the "victim", and in Spanish it is the other way around.