The HouseGuests that make up the top 50% of confessionals get declared to be the "main cast." For example if Glenn gets 25%, and the next most is Steve with 15%, and the next most is Cliff with 10%, then those 3 would be the "main cast."
BB12
Enzo Palumbo
Britney Haynes
Hayden Moss
Lane Elenburg
BB13
Rachel Reilly
Jeff Schroeder
Adam Poch
Dani Donato
Jordan Lloyd
BB14
Dan Gheesling
Frank Eudy
Ian Terry
Danielle Murphree
Britney Haynes