US/IOA doesn't use their marketing of characters the same way that Disney does. I mean, you will see the occassional characters standing to the side to sign autographs (Dora Dora the Explorer, Shrek, Fiona, Spiderman, Cat in the Hat, Popeye, Grinch, etc.) but most of the performers you'll see walking around will be geared more toward the older crowd (Marolyn Monroe, Egyptian Stilt Walkers, Zorro, hell, I even saw the Blues Brothers walking around). So if you're looking for characters that are old time favorites, you'll most likely find them randomly throughout the park rather than at some character breakfast.
To tell you the truth, if there was some form of character breakfast, I would not know what characters they would throw in there. Granted, Islands like Toon Lagoon, Marvel Super Hero Land, and Seuss Landing all have a wealth of characters but none that can signify both parks like Mickey. Hell two of the islands such as Jurassic Park and the Lost Continent don't have any central characters at all.
All in all, if you're looking for a character breakfast that is on par with disney, I do not think you'll find one here. Disney has perfected it!