For those who missed it:
The mystery puzzle was a team BLD variant. I'm not sure what it should be called, but I'm calling it "dueling team BLD" for now. Basically, we had several teams do regular team BLD first, and then we took the top two teams (four people) competing in another team BLD solve for one prize. The idea then was that you're competing not only against the other team, but also against your "teammate": the blindfolded team member was supposed to solve the cube, and the caller was supposed to solve it into the superflip. Whoever finished first (and in the correct position) would win.
As it happened, I think it would have been better to just let one team do the second round. The team of Brandon and Nathaniel beat Vincent and Chia-Wei basically by agreeing beforehand to let Nathaniel win--Nathaniel just did a regular solve, then called "do a superflip," and Brandon obliged. We tried it some more at dinner afterwards, though, and I had ridiculous amounts of fun. My favorite methods: 1) Solve into a position with between four and eight edges flipped, then either correct them or flip the others. 2) Roux. 3) Methods weirder than Roux. (Against Lucas, I solved all four F2L pairs first, without the cross, then did COLL and finished with M, U, and S, making sure to incorporate item (1) as well. For his part, he disobeyed some of my instructions, especially when I was telling him things like "flip all edges on L... okay, x'... okay, now flip all edges on D... now flip all edges in the S orbit...")
Oh, also, Lucas organized a mystery puzzle in which Jeremy had to write "Stanford" 20 times (since he'd misspelled it on the scramble sheets or something), and I had to write "Berkeley" 20 times. I won by 2-3 seconds, although someone who joined as a third or fourth competitor beat us both by quite a bit.