We were on the Sept. 19th Dream 4-day. Happy hours were listed every day in the app. We went to the 6-7pm Pink HH a couple of times where all champagne cocktails were 8 bucks instead of $12.50. There was also another one at 9pm which we skipped since we had late dinner seating. The sports bar also had HH which we missed but when we were there later for 70's music trivia, the guy next to us ordered wings which he said were good.
On Castaway Cay day, they had Mimosas for 5 bucks in the morning. Also had a special on Bloody Marys and screwdrivers but don't remember price.
There was one other bar on board that had HH each day, maybe Currents. Didn't go there.