It could be a budgeted platformer plus point and click game. However, Nintendo has been making a lot of platformers lately so it would probably get lost in the crowd.
Perhaps a light-hearted horror game like Luigi Mansion could work? Popo and Nana are separated and lost in an arctic mountain climbing trip to find the fabled purple eggplant for their archaeology research. They will have to try to find each other in the beginning and eventually team up. But being expert climbers, they are still determined to find the eggplant after being lost initially. And just like Resident Evil, if one of them dies, its game over.
The catch in this game is you play as Popo or Nana in the day and nighttime, scaling the mountain to find each other and later the eggplant. However, just because you play in the daytime doesn't mean its significant less scary. Occasionally, a wild blizzard will blow by blocking your vision with white snow which is how Popo and Nana got separated in the first place. Enemies will take this time to ambush you so you have to be ready with your trusty winter mallet to knock them out. Sometimes the wind gets too strong and will blow you out too, so you have to take cover before it hits.
But as nighttime approaches, you better find a checkpoint soon. One of your top priority in the daytime is to find a suitable shelter during the night. If you can find one before nighttime hits, the game will save, the screen fades to black, and you play the next day. But if you can't find one before dusk, nocturnal monsters will prey on you as you struggle through the entire night in a dark snowing mountain looking for one. If you find or build a shelter in a wrong place and stay there during the night, the game will fade to black as usual but then you will suddenly hear your shelter being broken apart and creatures snarling loudly. You will then have to fight off these creature and others along the way as you look for a more suitable shelter.