This is the penultimate episode of Pinky and the Brain. It took the series to a new level, and will always be the "best" in my opinion.
Before this, the series was just about Pinky and the Brain trying to take over the world. This episode revealed a sweeter side to the characters. All Pinky wants for Christmas is for Santa to give Brain the world. And right when Brain has the world in the palms of his hands, he gives it up in the spirit of Christmas.
While sacrificing none of its usual hilarity, this episode was a very touching scenario that went beyond 'taking over the world' and showed the meaning of friendship.
Excellent voice characterizations of Pinky and the Brain as usual by Rob Paulsen and Maurice LaMarche, this episode was a series best.