General Classifications of the Minor Characters seen on "The Big Bang Theory":
Aliens
Business Clerks
Girls Interested In Science
Goth Chicks
Medical Professionals
Miscellaneous People
Non-clerical professionals
Penny's Friends
Police/Guards
Professors/Academics
Sheldon's Bar Women
Sheldon's Roommate Applicants
Store Clerks
Train Passengers
Voice Overs
Waiters/Waitresses