Don't feel bad about that. When I was young I was watching cartoons in french, so I only discovered Tara Strong when I began to watch the show.
Well, there are several well known actors or comedians who make voice acting. Not only in movies. But since it was only for a gig, he probably said why not. Well, maybe we'll see him again. I kinda hope, though.
I'm sure fans still hope that David Tennant makes the Doctor's voice. Fat chance.