Rugrats: Castle Capers looks great. Personally, I think it's one of the best-looking GBA games I've played. The colors are very bright, vibrant and just pop right out at you. Everything reminded me of the old SNES games - you remember, the ones where they tried to squeeze every single color the machine could produce in the same screen. It may sound like a mess when I describe it - but seeing is believing. Each of the levels has something about them that just makes them feel alive, like the spinning gears in the Clock Work Babies level. Unfortunately, this doesn't carry over into every level. But for every bland level like Ali Baby and the 40 Fleas there's a great looking Sure Would Forest level. In the end, it all balances out nicely.
All of the Rugrats are present and look great. While they don't use any of this new fangled cel shading to make them look more like a real cartoon, they still resemble their cartoon counterparts. Each is animated very nicely, and has their little nuances, such as Dil's walker spinning around as he walks, to bring a smile to kid's faces (and probably some grown-ups too).
Anyone who has seen the show will instantly recognize the music. It can get repetitive, but it just has a fun feel to it that keeps it from getting annoying. Of course, the familiar Rugrats theme song is present, and if you listen closely, parts of it seem to echo through each of the levels. It's just really well done. The sound effects are a bit sparse though.