The other day, I was digging in the sand with a bunch of four-year-old boys. They were making sand castles by filling their buckets with wet sand, turning them over, and sitting on them. Then they'd get up and pick up the bucket, and there would be a sand castle. Since the process involves sitting and therefore the tuchus and they so like to say that word, they called the castles Tuchus Butt Castles.
I really like this phrase, but there aren't many opportunities to use it in day-to-day conversation. So I am advocating its use as an exclamation of surprise or dismay. For example:
Me: I'd like a large Cherry Coke, please.
Guy at the pizza place: I'm sorry, but the Cherry Coke is out of order.
Me: Well, tuchus butt castle!
Think it'll catch on?