We did the Baltic Capitals cruise two years ago and they did have a pirate night. They also were testing out the Frozen deck party (I thought it was rather lame...just a glorified sail away party for 20 minutes that Elsa and Anna only appeared in in the last couple of minutes). Saw it last Sept. twice on a b2b med/trans and we had two pirate nights as well. The Frozen event was better (more "snow" and characters), but without a special buffet. The dinner menu each time was Frozen-inspired, as were the decorations around the ship, a special scavenger hunt, and redo of one of the bars into the Snuggly Duckling.
As I said, we also had pirate nights, complete with deck show, buffet and costumes.
DCL may have cut out pirates on this cruise...give them a call. As far as I know, the only non-pirate cruises are to Alaska and maybe Norway where it is too bright at 9:30 or so at night for the fireworks to show up. By the way, the TANGLED show was awesome.