Remember, "formal" on the ship is not too much of dressing up......some peoples' ideas of formal is ridiculous of course but a nice sportcoat, collared shirt and slacks (tie preferably) is perfectly acceptable, so don't worry about having to dress up too much.
The menu on formal night is pretty special. It's usually the most desirable items.....I think the Lobster is on the menu that night for instance.
Holiday 5-day Western Caribbean
Liberty 8 day Western