"El bebé" is the subject of the sentence. "Le" and "a Pablo" are both indirect object. In Spanish, indirect object must be preceded by "a", except when you replace it by "me, te, le, nos, os, les, se".
You could say "le gusta el bebé" but to say "a Pablo gusta el bebé" would be incorrect, because "gustar" is a reflexive verb and requires use of a reflexive pronoun.
I hope it helps.