You are all wrong. Heehee.
I'll give you more time.
This was the last attraction that Walt came up with the concept for, in 1966, before he died. The attraction obviously opened later than that.
Walt came up with the concept for Space Mountain in the early 60's. All the ones you guys mention took a long time to build, and were thought of before this attraction. Big Thunder was a Tony Baxter project, and I don't think it was a Walt project at all.
I'll admit there's a slight trick to the question.
I told GD the answer, he's not allowed to respond.
