We were accidentally on a "polka cruise" a couple of years ago on the Sky Princess. It was not a polka themed cruise sponsored by Princess. It was a polka group (Mollie B) that was comprised of a lot of people/members. No, they did not take over the Princess Theatre but they did close off the Vista Lounge every night for their event. This did impact our entertainment as it eliminated that venue for the rest of us and any subsequent entertainment. If I recall correctly they also closed one of the bars for their group each evening. Even if you wanted to enjoy polka music, you were not able to participate unless you were in their club. As a result, we didn't hear any polka music at all. I guess if you know what to expect, go with an open mind. Having experienced this once, I wouldn't want to do it again.