Combine Psychonauts with Penny Arcade Adventures, and you get Costume Quest: a light, fun, adventure/rpg.
In CC, you control one of a set of twin kids (either the boy or the girl -- it's up to you), and set off on a fantastic adventure on Halloween night. The game world intentionally blurs the line between reality and a sinister plot filled with monsters and an evil witch, bent on collecting as much candy as possible for the big boss. Now reading just that, you'll think, "is this a game just for kids?" The answer is it _is_ a game for kids, _and_ a game for adults. It's for anyone with any sense of whimsy, and it's fun whether you're into RPGs or adventure games.
The game world is really immersive -- everything looks great, the world is populated with other people that each have bits of personality to lend to the world, and lots of great attention to detail throughout. The music, as always with Double Fine, is a major piece of the environment -- it's whimsical and very well done, like everything in this game.
The "RPG" elements are pretty basic: you will "level-up" as you gain experience by fighting bad guys, which increases your health and ability to do damage. You'll also collect stickers and trading cards as you go to change your abilities in combat or to trade with NPCs.
You collect Halloween costumes, which come into play during combat -- each costume has different attacks and defenses, some will better protect your party, some are more focused on attack, etc. You'll outfit your party of up to 4 kids in these costumes, and can do so any time -- they also play into the adventure puzzle elements of the game.
The "adventure" side is essentially revolving around doing a simple questing, such as finding a key ingredient for a pie maker, locating lost trading cards, and other things you'd expect kids and neighborhood adults to need/want.
The game is linear for the most part, but in each larger area, you are certainly encouraged to explore every nook and cranny for costume pieces, trading cards, etc.
Combat occurs when you either knock on a house where a monster has taken over the residence, or when you intentionally bump into a wandering monster on the main game screen. When you enter combat, your cute little kids in their cardboard costumes morph into gigantic, terrifying versions of what their costumes represent, and the monsters do as well. You can really picture in the kids' imaginations that they are picturing the epic versions of their costumes in their minds' eyes. Combat is turn-based, and attacks use one of a few different mechanisms from quick-time events to rapid presses of a certain button. The combat reminded me a lot of Penny Arcade Adventures. As you fight, you can charge up each character's special ability, which might be a super attack, a heal spell, etc. You will fight a few bosses as well. Overall, though, the combat is really pretty easy.
The good:
* Terrific looking, well animated, cell-shaded, 3d visuals. Everything is colorful and distinctive looking, with an intentionally "cartoony" feel .
* Lots of little things to do throughout, from collecting candy and trading cards, to finishing small side-quests.
* Good length -- the game is pretty simple, and clocks in at 6-8 hours, so it's just long enough to be satisfying, but not so long as to get tedious. The PC version includes the console DLC for free, which is nice, and adds another couple of hours.
* Fantastic audio -- the music is terrific, and the voice overs are all well done.
* Variety in game areas -- you'll travel to several different areas in the game, and each looks and feels different than the others.
The not-so-good:
* Combat could've used a little more variety, or been optionally a little harder. Once you reach the mid point of the game, combat is almost an automatic win.
* No in-game map (or if there was one in there, I didn't find it). The areas are somewhat maze-like, and large, so it can get tedious wandering to find something specific.
Overall, it's a terrific, light-hearted adventure/rpg that just about any gamer will enjoy.