Something has been bothering me. In all the KH games the secret boss has foreshadowed the next game:

1) KH- Mysterious Figure- was Xemnas the main antagonist from KH2

2) KH2 final mix- the Lingering Will turned out to. Be Terra a main protagonist from BBS

3) BBS- Mysterious figure- turned out to be Young Xehanort, the main Antaginist from 3d.

 

Now we come to 3d where the secret boss was Julius. The pattern seemed to have ended. I mean it didn't seem to add up to foreshadow the plot. However Julius as has been mentioned comes from the short ' The Runaway Brain'. I won't spoil the complete plot, however it does portray Mickey in a ' darker sense'. Now we have been told that after 3d Mickey confesses secrets he had previously kept hidden.

 

Let's go back to to 358/2 days and KH2. Mickey is not unfamiliar to making secrets, however as in the case of Riku, that was almost understandable. Now if people remember in the original BBS Volume 2 trailer we saw Mickey in the Realm of Darkness with the Star Seeker keyblade, so one would feel Mickey either ran into Aqua or found out what happened. Now seeing as they are friends, you'd think she'd be rescued too etc

 

So that hints at something utterly tragic potentially in the makings here, now going back to the original theme about secret bosses foreshadowing, could Julius represent the ' dark secret' Mickey is going to reveal to Sora etc?

 

If so, this begs more issues, such as what does he know? Why didn't she escape? Has she escaped? What does Xehanort know? Who will save her? The list does go on.

 

Thanks for reading and I hope this makes sense to people

To be fair all the secret bosses in those games where original characters while this secret boss was a Disney character so I don't think he will be showing up in any other kind of Kingdom Hearts games after Dream Drop Distance.  As to the whole Mickey possibly running into Aqua while he was in the Realm of Darkness there has to be a reason as to why Aqua didn't leave with him but then again if you remember Mickey was still in the Realm of Darkness at the end of Kingdom Hearts to help seal the door with Sora.  And with that being said we actually don't even know how Mickey found his way out of the Realm of Darkness and to Castle Oblivion

Calling it right now: Mickey was once turned into a heartless and has a nobody roaming around. You heard it here first.

Maybe Mickey didn't have the power to get all three (Him+Riku+Aqua) out of there??? Or maybe she didn't want to leave until she knew Ven was safe in the outside world?

Maybe, the secret that Mickey is keeping is that his nobody is Oswald The Lucky Rabbit. However, because he's been trapped in the realm of darkness by none other than Mickey, he wants to find him as well as Aqua.