Somebody may have already mentioned this, because I didn't check the entire thread, but if you can track this down (easier said than done, I know), you might want to try Chibi-Robo. That was the last GameCube game I bought, shortly before the Wii launch. I took a risk based on one very complimentary review in a magazine, and I absolutely loved it.
It's a little slow to get going, but once it does, you'll have a great time exploring the house and soaking up the game's immense charm. Comparisons have been made with Majora's Mask, and though that didn't occur to me at the time, the connection makes a lot of sense with regard to the side quests.