The phrase "original cast" refers to the group of actors who first performed in a play, musical, or movie when it was first produced or released. Full definition
Edge of Tomorrow 2 has a title and a returning original cast member. (screenrant.com)
The developers managed to secure the entire original cast of the series so it will be nonstop nostalgia the whole way through! (engagedfamilygaming.com)
I hear talks are underway with other original cast members to return. (deadline.com)