The games are representations of Croc's memory.
(Providing maybe a bit of Fridge Brilliance
!) Everything in Croc LotG is mainly silent, especially in the cut-scenes, with the odd vocal expression. When it comes to the 2nd game, Croc starts off remembering odd words like Rufus' "Totally"s but then in the mainland he's talking fluent... simlish. When it comes to the end his vocabulary and his remembrance of others' is top-notch. He even manages a "Oh, MAMA!" and "Pater"; shaking his Dad's hand (which is quite a complex memory - motor dependant) and even flying the plane over. Things have bypassed mere instinct and Croc is becoming a very intelligent crocodile.