Let's remember the Jedi never learn Darth Maul's (now Darth Grievous') name in Episode I. So it's not like Obi-Wan would be, "You're Darth MAUL!?!?" Keeping this in mind allows Maul to be referred to as Grievous in Episode I, and Grievous be referred to as Grievous in Episode III without any kind of reveal necessary until his confrontation with Obi-Wan. And dialogue hints would be best dropped in earlier in the film, such as when Anakin and Obi-Wan surround him on the bridge, Grievous can say something like, "This feels familiar, but not this time Kenobi!" as he jumps out the window. A shame he doesn't fight Anakin and Obi-Wan a bit with his double-sided vibroblade; that would be an awesome connection, but I don't think any amount of special effects wizardry an pull that off. The dialogue has to be vauge enough to where Obi-Wan doesn't realize who it is he's fighting until that key moment in the duel, at which point we need a brilliant line to tie it all together. Unfortunately the only thing I can think of at the moment is the atrocious "I have killed your master! Now it is your turn to die young Jedi!" from the Episode I video game.

Just an update on that Anakin/Obi-Wan duel, I put it together a LONG time ago and looking over it, there's a lot I'd like to refine before sharing it with everyone, so it'll be next week before I upload it. Speaking of which, what service do you guys suggest I use for uploading clips?