Unlocked after you collect 45 combined stars in the previous locations. Each location has various missions that you can earn up to 3* in and 5 smaller tasks that are each worth 1*
Smaller Tasks:
-Collect SKATE
-Collect COMBO (obviously must be done in one combo)
-Collect the DVD
-Collect the VHS Tape
-Level specific item to break (It's the Tiki Guys at the Beach as an example).
Not going to link individual guides for each mission as it would be overkill in this solution. Just giving you all a target so you know when this level will be unlocked.
Note: You DO NOT have to complete every mission and task in the first few areas to get here. There is plenty of room to get an array of stars and skip some all together.