It's not new. It's been going on at least 4 years. Every time we travel with DS, almost 3, we use the pack n play and it always has the fitted mickey mouse sheet with it. They don't provide the small baby blankets, though. you need to bring those.
I am at the Beach Club Villas now and just went to check the sheet and yes, it is a fitted sheet specifically for the pack and play...It is cute with Disney characters on it...