Were you watching the actual episode on Cartoon Network or online? Because there's versions of new episodes floating around that have an old set of credits from a Grand Festival episode tacked on at the end of it. (if the supporting cast you see is Bella Hudson, Mike Pollock, Billy Regan, Kayzie Rogers, Melissa Hope and Hilary Thomas... it's not the right credits)What I found weirder was that Jamie McGonnigal wasn't listed in the credits, even though Barry was there.
Of course, TPCi's made mistakes in their credits before. Julian Rebolledo (Paul) not being credited in DP100 and Sean Schemmel not being credited in DP117 are two examples I know of off-hand.