If you're over in the Marvel area, they have characters come out every so often- I saw Spider-Man, Wolverine, Doctor Doom, and the Green Goblin.
In Suessland we saw the Grinch, the Cat in the Hat, and the Things.
When we went, at the end of the Shrek ride you could get pics with Shrek and human Princess Fiona, and at the end of Minions there was a Minion character to pose with.
There was the driver of the Knight Bus, and the Hogwarts Express Conductor, and you can get close to one of the bankers in Gringott's in one area.
I know there were more, but over two days we didn't get very far.