More info from Ryan.Charlie crossover confirmed. Henry Ian Cusick and Dominic Monaghan were rehearsing a quick scene. Charlie is playing guitar on a street corner, and Desmond comes up and talks to him. It seems as if he has an epiphany. "This is happening!" Hmm.
The crossover, of course, is just a bit of whimsy. The main scene is Desmond storming out of Widmore Industries and throwing his tie to the ground. Guess a meeting didn't go well. Source: Ryan@The Transmission