understudies
n. 預備演員,替角,代替之人( understudy的名詞複數 )
An actor's or actress's understudy is the person who has learned their part in a play and can act the part if the actor or actress is ill.
He was an understudy to Charlie Chaplin on a tour of the USA.
他是查理·卓別麟美國巡演期間的替角兒。