Here are the passwords for every level:
Casper High- You don't need one.
Fenton Lab- JAZMINE
Vlad's Chateu- PAULINA
Bikini Bottom- SKULKER
Chum Bucket- PATRICK
Plankton- MERMIAD
Timmy's Home- SCALLOP
Dimmsdale Dump- BABYSIT
Crocker's Locker Room- GODDARD
Jimmy's Lab- ESTEVEZ
Subterranean Caves- LIBERTY
Prof. Calamutis' Lab- SKYLARK