When I get older, and get a house and kids etc, I definitely want my kids to have to gather crests all over the house to be able to open the door to the backyard.

Kid: Dad, I wanna go play on the swings with Barney and Marie.
Me: Seems like you're missing the Moon Crest, sweetie. Did you check the snake attic?

Even better. I'll infect one of them with a venomous poison, and send his siblings to run across to the other side of the house to find the serum I've hidden somewhere. Maybe I'll give them broken radios so they can communicate.