'The Standbys' shines spotlight on Broadway actors who may never get on stage

They learn the lines of a Broadway lead, make sure they have all the moves down, and get fitted for their costumes ... and may never take the stage. That is the job of a Broadway standby. These hard-working actors are the subject of a new documentary “The Standbys” which shines the spotlight on those waiting in the wings to jump in at a moment’s notice to make sure the show always goes on.

“I think if you've been to a Broadway show, and that program is open, and the insert has fallen out that says at this performance the role of so-and-so will be played by somebody else, and you feel the audience groan, and be like 'Oh, I'm not going to see the person that I wanted to see,' it's like, what's the other side of that story?" director Stephanie Riggs told FOX411 "What are the people that are waiting in the wings ready to go on at that moment’s notice, what’s their story?”

Actor Ben Crawford, a standby for Broadway’s “Shrek the Musical,” is featured in Riggs' documentary. Crawford shared what that kind of audience reaction feels like from a standby’s point of view.

"If you hear that disappointment, it's like, okay, well let me prove you wrong," Crawford said. "You kind of have to take that in with a little bit of an edge as you're going in, because a lot of times you are going to be looked down on a little bit because they've spent this money and they expected the person who's done it every night to go in and do the show. So the best way is to prepare yourself as much as you can to put on a great performance.”

It can be very rewarding if you do indeed put on that great performance.  Actors like Crawford know everyone has to start somewhere, and in such a competitive business, he says getting a job as a standby is a good steady gig.

“It's great money, it's a Broadway salary, and you're at the theater," he said. “I think the hardest thing as a standby is you're not going on every night. So that can be the hardest thing. We do this because we are passionate about it and we love it, and when you’re that close, yet so far away from it, it’s like dangling that carrot in front of you. So it can have that artistic frustration.”

Paying your dues can pay off. Crawford eventually took over as the lead in “Shrek,” though he says that transition isn’t common. “I was very fortunate to be able to do that. A lot of times with a show, a well-known actor leaves and they are going to replace them with another well-known actor," he said. "So I was very fortunate that I was able to jump in and actually make the part my own for a while.”

Riggs found an encouraging list of celebrities who started as understudies or standbys. “Natalie Portman, Britney Spears, Kevin Spacey, Glenn Close, these are all names that were one time understudies or standbys," she said.

The film also features another behind-the-scenes job called a 'swing.'  “A lot of times they have to be able to cover the entire range, vocal range, as well as the dance range, of multiple parts in the show. The swings are the ones that I would say understudy all of the ensemble roles in the show," she said. "So they have to be able to, if that understudy goes up to the lead, they fill in for that ensemble member. So, a very talented group of people that perhaps don’t get the credit that they are due.”

“The Standbys” heads to theaters in limited release February 21st and is available video on demand soon after.