I was incredibly excited when he showed up in the first long trailer. When playing, I thought Young Xehanort was him ("I see you're still afraid of the darkness" in Notre Dame), only to get to Monstro to see the full scene in the trailer and TWTNW completely dashing that idea.

 

Why did he just show up and bother off, other than to give Riku a chance to monologue? Could his absence be significant in a similar way to Kairi's?

I was incredibly excited when he showed up in the first long trailer. When playing, I thought Young Xehanort was him ("I see you're still afraid of the darkness" in Notre Dame), only to get to Monstro to see the full scene in the trailer and TWTNW completely dashing that idea.

 

Why did he just show up and bother off, other than to give Riku a chance to monologue? Could his absence be significant in a similar way to Kairi's?

 

Not sure I understand what you mean, but to clarify I dont think that was Repliku, I am pretty sure that was Ansem SoD that was pulled from time using Riku's body...

Not sure I understand what you mean, but to clarify I dont think that was Repliku, I am pretty sure that was Ansem SoD that was pulled from time using Riku's body...

 

Sorry, that did come out pretty garbled.

 

In CoM, Repliku was like a broken record with saying "You're afraid of the Darkness!". When young Xehanort said something similar in the final part of City of Bells, I thought Repliku had pulled a Xion and changed his face. But that isn't very relevant, since in Prankster's paradise, Repliku shows up to help Pinnochio and leaves, and then Riku talks about him in metaphors. What's the point of him showing up that once?

I'll just quote myself from a similar thread:

 

I'm thinking it was just a dream representation of Riku while he was working with Maleficent in KH1. He kidnapped Pinocchio then, and now while he's trying to make up for all the bad things he did. Riku said it himself. Several persons has come to remind him of his past, first it was the seeker of darkness (Ansem), then there was a dark replica (Riku Replica) and now he faced himself.

 

Riku kidnapped Pinocchio in KH1, the Riku we see in Monstro might have been a dream version of Riku from KH1, haunting him yet again.

well right after you see that riku AKA Replac riku you get the cronical of Chain of memories.