Characters that have had several voice actors, like Lincoln Loud and Ren, are voiced by their most recent actor, with the exception of Leonardo, Michelangelo and Shredder, who are voiced by their actors from the 1980s cartoon. Those seven are Nigel Thornberry, Oblina, April O'Neil, Reptar, Aang, Toph and Powdered Toast Man.
Of the twenty-three characters currently available, only seven are not voiced by their actor from their respective cartoon.
Another free update today added items and, more importantly, addressed the notable absence of voice acting from a cartoon-themed game.
Besides regular balance patches, a number of free content updates have been made, adding things like alternate costumes, a new stage based on Double Dare, or new characters (namely, Garfield and Shredder). Nickelodeon All-Star Brawl has received a surprising amount of support post-launch.