Good co-op DS games?

A while ago, my gf mentioned how much she likes Tetris, so I showed her Meteos on the DS. She was instantly addicted and couldn't get enough of the game. So for Christmas, I want to get her a DS Lite, Meteos, and another game.

However, I'm having trouble coming up with another good game--I'd really like to get her another multiplayer game; something we can play together. She's not all that into gaming, so any other head-to-head game probably wouldn't be too much fun for her.

So are there any good co-op games for the DS? How is the Crystal Chronicles game? It seems like it would be perfect, but it looks like it got mixed reviews.

I'll second Clubhouse games. If your GF likes card games, board games such as chess and checkers, you two may have fun playing that. Another upside is that you only need one cart but alot of people seem to have troubles finding this game though.

Just incase you don't know you'll need two copies of Final Fantasy Crystal Chronicles to play two players.  

Yeah, I know that I'll also need a copy of Ring of Fates for myself. I had completely forgotten about Clubhouse Games; that's also a game I've wanted for myself.

I think the answer might be both, haha. Her birthday is January 19th, so I'll probably get her CHG for Christmas and then ask if RoF would be something she'd be interested in after I get her the DS.

Tetris DS is a definateMARIO-FREAKO

*gasp* you stole my pic:O haha, i dont care anyways:P id say bomberman

Contra 4, if she's up to the difficulty.

I heard of some game called Cookie and Cream that's a co-op game, but haven't really seen it anywhere.