I think being over the top as opposed to being "arrogant and self-centered" in a playful manner are two different things.
Compare these two videos...both Darth Maul (different ones, I assume). Now, mind you, I am not commenting on either one, but merely pointing out how pressing too much of "staying in character" can actually lead to off putting experiences (compare the first to the second).
Darth Maul pushes a mentally disabled kid (again I want to be clear, I am NOT judging the CM playing him at all...the kid was not being supervised, but it still could have been handled better. It's quite obvious Darth Maul was stuck in his character when you observe how previous characters interacted with the kid.)
And this
Then again, having done work in costumes, and been attacked by kids (kicked in the privates, punched, bitten, list goes on), I can understand why it can be very frustrating work. Disney costume characters have it easy compared to many others.
Try being a hockey mascot (which I was for a while)...where you have drunk adults actually TELLING your kids to kick you in the butt! (yeah, nice show Greenville, SC...your fans are terrible!)