Yup, he forgot, as it seems. And I like that part of the storyline very much, I said I found the reactions of both characters very realistic. But still, it is a very much creepy scene if you imagine it from a first person view, pretending not knowing the events that predate it.
I think that sometimes Naija can be a frightening character. She's practically a dangerous predator. The beast form is good symbol of that aspect, that's why I liked a previous fanart depicting her as repulsive monster. Sometimes she does things, that are, let's just say, not too environmentally sensitive. One of the oddest scene's of the game is when you venture into the nest of Nautilus Prime, kill the big momma, and raise a little nautilus made orphan by your own actions.
I think, this lack of strict definiton of good and evil in the characters of Aquaria is an important element of the story. Think of the Creator, Naija's mom, Naija herself. Also, we are the most cruel predators of Earth, yet we don't like seeing ourselves like this. In the end, this duality of the characters becomes a sensitive description of the nature of humanity.
That is why I would hate if this aspect of Aquaria never got adressed. It's sure relaxing to view her as the cute little girl that she is, but the other aspects of her character are the things that make her really interesting, and not just another reincarnation of disney's little mermaid.
Its interesting, Naija questions her own motivations at various points as well... and often times when her motivation seems clear, it becomes more questionable if what she's doing is necessarily good or not.
Its interesting to see people's reactions to various things in the game. I was recently reflecting on the ending, and how its generally assumed that Naija's family with Li is a happy one. However, there isn't really much evidence to support what the relationship would be like, whether or not it was actually happy. Right after the scene with the baby, there's the pan back up to the original cave and Naija's line about:
"I longed for the feeling of discovering new waters - striving for a destination that lay just beyond the next wave..."
then in her cave, as she's sitting on the rock just like at the beginning of the game
"...it would never come again"
That was in part intended to mirror how the player might feel at the end of the game, knowing that its ending... and realizing that they'll never be able to play it for the first time again.
But it also brings up some interesting questions about Naija; is she really happy staying at home "burping babies and changing diapers"?
Another interesting angle is the theme of feminism. You could look at the game as Naija finding her own way and defeating the 'Creator', a powerful male figure, who was idealizing her as his companion. Naija also leads Li around for the game and is the one who rescues him, which is a flip on the traditional idea of "saving the princess".
However, Naija ends up settling down with Li and becoming a mother, which suggests that she's not totally independent.
In the extended ending, Mia returns and also brings back the idea of female independence, but this time to a further extreme. Also, Naija is enslaved to her in that sequence, so it suggests that perhaps the female power has taken over and is now the force that has to be overthrown.
The Creator I view as being mainly an innocent being, granted an immense amount of power - and he is not aware of how to be responsible for it.
Standard Disclaimer: These are my own views. I think there's room for multiple interpretations of the game, and I don't intend to disrupt anyone else's views on the matter by sharing mine. 