It was only a matter of time. Diet Coke + Mentos = geyser. Everyone knows this by now. Of course, in the name of science (naturally), it was only a matter of time before somebody took the idea to the far end of sanity: as a performance art piece inspired by the fountains at The Bellagio.
Hence, 200 liters of Diet Coke + 523 Mentos = you wondering, "Rehearsals for this must have sucked."
And just remember what our friend Lord Fanny used to say: "Nothing exceeds like excess."