The Secret Saturdays: Beasts of the 5th Sun comes incredibly close to being one of the DS's better looking 2D games. The game retains the show's unique angular style, while adding a bit of pseudo-3D in the mix - mostly for a bit of added visual depth. All of the show's characters are recognizable and the animation is incredibly smooth, particularly when it comes to transitional animations. For instance, Zak easily flows from one swinging animation to another without any sort of awkwardness.
Both the sound and sound effects go right in time with the rest of the package. I've only seen the show a few times, so I can't say if it is music from the show, but either way it sounds good. Sound effects hit all the right areas; they're loud, clear and never get annoying. The game even includes some voicework from the show.