I've heard Bakugan mentioned in this house already!
But, if you're looking for ideas, check these out!
I love that your niece appreciates Princess Leia! I read just the other day that the first three Star Wars movies beat the recent three hands down. :)
I love the pirate idea! I want to be a pirate too!
Aww! Mine haven't dressed up in their costumes for a couple of years. I'm mean and I don't let them wear their costumes before Halloween (because I know they'd be falling apart by the time Halloween arrived! LOL) But, I've had Power Ranges and ninjas running around here for a couple of years.
I hope you'll post pictures of Wario & Yoshi! My 9 & 12 year olds still love playing Mario Smash Brothers (Or something like that) on the Wii. So, don't expect them to disappear anytime soon in your house! ;-)
Last year's costumes!