Balthier already had a cameo in a Final Fantasy Tactics game. Now it’s Vaan and Penelo’s turn to act as guest characters. In Final Fantasy Tactics A2 they look a little older and they each have special jobs. Vaan is a sky pirate and one of his skills acts like mug (capture in Final Fantasy VI). He can attack an enemy and steal at the same time. Penelo is a dancer and it looks like her skill list may be similar to the Final Fantasy Tactics class. She can do the Polka Polka dance which lowers the attack value of the on screen monsters.
While it is neat to see Vaan again in new threads the timeline is awfully confusing. A younger looking Balthier was in Final Fantasy Tactics: The Lion War where he met Ramza and Luso. Luso is the protagonist of Final Fantasy Tactics A2 where he runs into an older Vaan and Penelo. The events must take place sometime after Final Fantasy XII: Revenant Wings then. And logically, Final Fantasy Tactics: The Lion War occurs way before A2. So… just how old was Luso when he met Ramza and Balthier? 10? No wonder his Monster Hunter job class doesn’t have any special skills in Final Fantasy Tactics: The Lion War!
