Complex sentence: Then his neighbour comes out and says it's for her, so Pingu grabs the parcel back and gives it to Mother, who is delighted to get the letter, as it's an invitation to a wedding.
Split into simpler sentences: Then his neighbour comes out and says it's for her, so Pingu grabs the parcel back and gives it to her. Mother is delighted to get the letter, as it's an invitation to a wedding.