They did bring back some classic villains like Mojo Jojo, Princess. Fuzzy Lumpkin, and the Gangreen Gang, though they really didn't do much. Most of the Gang didn't even have lines, they were just window dressing. They tried to do too much at once with that episode. The could have easily dropped most of the baddies (why were they sharing a cell, anyhow?) and focused more on Him's scheme.
Oh boi.You know, ever since I was little, I always imagined Buttercup being a caretaker. Always thought it would be something out of her element. Anyway. What is it with this series obsession with Buttercup?