World Key

After the latest holiday update, now, instead of stars, you need world keys. World keys are golden keys, with clock arrows and a portal in the hole of the key. It is unknown how you get them for right now except for them being given.

Use
It can be used to unlock any world, as the description said when you get it. So you could go to any world in any order, such as Far Future (Update coming soon!), Wild West, etc. as well as any other combination.