Johnny Rockets is a 50's style diner. They have burgers, fries, onion rings, cherry flavored sodas (my favorite, just like they used to do it with the flavored syrup put in the fountain soda). They also have great shakes.
I know they have them on the voyager class ships. Not sure if they are on any others.
They do charge a cover charge of $3.95 per person which includes your food. There is an additional charge for sodas or shakes.
If you are a member of the Crown and Anchor club they give you coupons to cover the cover charge. The only thing you pay for is your sodas and extra tip if you wish. We went at 11:00 one night and were the only ones in there. Needless to say, we got great service. We tipped the guy an extra $5.00. This was still a deal. Food was also very good. Didn't really care for Johnny Rockets when I had tried it before at home. Maybe it was the sea air (or I should say wind). Try it if you have the chance.