The dancers were dressed in their 'national costumes'. [=the clothing that is traditional in their countries]
If all the actors are 'in costume', we're ready to begin.
The waiters were all 'in' ancient Roman 'costume'.
(..) $ gross. Less Social Security, less unemployment insurance, - less Santa training... - Santa training? less costume purchase, less beard rental, less Christmas club. - But-- But-- - See ya next year. - Ohh! - Come on, Dad. Let's go home. (..)1989 TvShow: The Simpsons Title: Simpsons Roasting on an Open Fire Season: 1 Episode 1