Once In A Lifetime is a huge comedy, with more than 30 speaking roles (more than many musicals). Here is a complete listing.
| George Lewis | A young vaudeville actor. Good natured, but not very smart. |
| May Daniels | A comon-sense vaudeville actress with a dry sense of humor. |
| Jerry Hyland | A magnetic young vaudeville actor. Sharp, funny, looking for a break. |
| The Porter | An observer of life, very dry sense of humour. |
| Helen Hobart | Aggressive, talkative gossip columnist. |
| Susan Walker | A small town girl who wants to be an actress. Not very talented |
| Cigarette Girl | Staff at a Hollywood hotel, wants to be in pictures |
| Coat Check Girl | Staff at a Hollywood hotel, wants to be in pictures |
| Phyllis Fontaine | A silent movie star, whose voice sound like nails on a blackboard. |
| Miss Fontaine's Maid | Wants to be in pictures |
| Florabell Leigh | Another silent movie star whose voice sound like nails on a blackboard |
| Miss Leigh's Maid | Wants to be in pictures |
| Miss Leigh's Chauffeur | Wants to be in pictures |
| Bellboy | Staff at a Hollywood hotel, wants to be in pictures |
| Mrs. Walker | Susan's mother, very protective |
| Ernest | Head Waiter at a Hollywood hotel |
| Herman Gloguer | Good natured, nervous moving picture producer. |
| Miss Leighton | The studio receiptionist. Very ditzy . |
| Lawrence Vail | A serious playwight from New York |
| Weisskopf | A studio executive |
| Meterstein | A studio executive |
| First Page | A studio page |
| Second Page | A studio page |
| Secenario Writer One | Studio employee |
| Secenario Writer Two | Studio employee |
| Secenario Writer Three | Studio employee |
| Rudolph Kammerling | A brusque, exicable German |
| First Electrician | Studio employee |
| Second Electrician | Studio employee |
| A Voice Pupil | An Actress |
| Mr. Flick | Studio employee |
| Miss Chasen | Studio employee |
| First Camerman | Studio employee |
| Second Camerman | Studio employee |
| The Bishop | A not so holy actor |
| The First Bridesmaid | Actress on a film |
| The Second Bridesmaid | Actress on a film |
| The Third Bridesmaid | Actress on a film |
| The Fourth Bridesmaid | Actress on a film |
| The Fifth Bridesmaid | Actress on a film |
| The Sixth Bridesmaid | Actress on a film |
| Script Girl | Studio employee |
| George's Secretary | Studio employee |
| Mixer | Studio employee |
| 1st Light Man | Studio employee |
| 2nd Light Man | Studio employee |
| Truckman | Studio employee |
Marin Summer Theater (MST) is an award winning non-profit theater company for students of performing arts between the ages of 13 and 23. The MST company prepares and presents three fully-staged productions in a six-week summer season. MST's mission is threefold: To present exciting, professional quality drama, musical theater and musical revue productions; to keep tuition as low as possible so that cost is not a barrier to participation; to create a diverse company of college and high school students.