The cast of Study - 2012 includes: Paolo Benetazzo as The student
The cast of Sleep Study - 2010 includes: Kerri Lendo
The cast of Field Study - 2013 includes: Olaf Marchwicki
The cast of Study Haul - 2010 includes: Jianna Justice
The cast of How Not to Study - 2011 includes: Harley Centner Jocelyn Kreiger
Are you talking about an understudy? Understudies are people who come to rehearsals and then if the actor that was formerly hired cannot perform (due to sickness, quitting, ect.) then the understudy takes their part. I think that they are called understudies because they study the actor's lines (hence study) and are underneath the position of the actor. I hope I helped.
The cast of Study Date - 2010 includes: Lexi Sakowitz as Ella
The cast of Welcome to My Study - 2007 includes: Mitch Magee as Mitchell
The cast of Study Session - 2007 includes: Abby Gerdts as Karen
The cast of A Study in Sociology - 1913 includes: Harry Spingler as Phillip
The cast of A Study in Red - 2010 includes: Krista Webb as The Painter
The cast of The Study - 2011 includes: Nick Gylaw Lizzy Mace Heather Yeadon