David Selby and Craig Wallace in the Ford’s Theatre world premiere production of ‘Necessary Sacrifices.’ (T. Charles Erickson)

Wednesday, Jan. 18. In Milwaukee, Washington actor Craig Wallace is rehearsing his supporting role in “To Kill a Mockingbird.” Meanwhile in Washington, David Emerson Toney, one of the leads in Ford’s Theatre’s “Necessary Sacrifices” — essentially a two-character world premiere about Abraham Lincoln and Frederick Douglass — is too ill to continue. Performances are scheduled to begin in two days.

From Ford’s, the call goes out.

Craig . . . Duuude. Little emergency here. Can you maybe, um, come play Douglass for us? Huge part, yeah. And could you be ready for audiences in, oh, say, a week?

Wallace, whose track record includes roles on most of Washington’s major stages, was game, and with the blessing of “Mockingbird” director Aaron Posner he was on a plane the next day. To create at least a sliver of working time, Ford’s canceled four preview performances and postponed the formal opening of “Necessary Sacrifices” by a week. Script in hand, Wallace was onstage as Douglass six days later.

“It’s insane,” Wallace says by phone from Ford’s, briefly peeling himself away from line-learning at the end of last week.

Enormous changes at the last minute have been part of theater forever. Still, Washington stages have endured a spate of switchouts lately. The offstage drama in November alone:

●“The Sound of Music,” Olney Theatre Center. Monica Lijewski, cast as the Mother Abbess, falls offstage into the orchestra pit during rehearsal. (Lijewski was seriously injured and is still recovering; see the open Facebook page “Friends of Monica Lijewski.”) Channez McQuay, already in the cast as another nun, fills in.

●“You, Nero,” Arena Stage. Marc Vietor departs as Scribonius, the narrator of Amy Freed’s comedy about politics and art in ancient Rome. (The reason is not announced.) Four preview performances are canceled. Jeff McCarthy, who played the part at Berkeley Repertory Theatre, takes over.

●“Much Ado About Nothing,” Shakespeare Theatre Company. Veanne Cox leaves the leading role of Beatrice in rehearsals; “artistic differences” are cited. Ten days before performances start, Kathryn Meisle is brought on. The really lucky part: Meisle (pronounced MIZE-lee) just finished playing Beatrice at New Jersey’s Two River Theatre Company.

At least the New York-based Meisle had done the last-minute leap-in before. Once upon a time Meisle, who broke her foot last summer, was thrust into Paul Rudnik’s “The Most Fabulous Story Ever Told,” taking the stage a mere 24 hours after being hired. She replaced Jenny Bacon, who had broken her foot.

Coincidentally, that very week, Christmas 1998, Bebe Neuwirth withdrew from the new Kander and Ebb musical “Over and Over” at Signature Theatre. Sherie Rene Scott, then at the beginning of a productive Broadway career — “Aida,” “The Little Mermaid,” etc. — was hired to take over.

It happens.

Mark Ramont, currently directing “Next Fall” at the Round House Theatre, was working on an Upstate New York summer production of Tennessee Williams’s “The Glass Menagerie” when his leading lady up and quit.

“Left a note, took the rental car,” Ramont says. He called a friend in Pennsylvania, who got through her first performances with lines being fed to her through an earpiece.

When Round House co-produced “The Trip to Bountiful” last year with the Cleveland Playhouse, a supporting actor was replaced a day before the first performances. According to Round House Producing Artistic Director Blake Robison, Howard Overshown learned the part in 48 hours.

“And he was great,” Robison says.

In 2008, Shakespeare Theatre Company Artistic Director Michael Kahn scheduled “Julius Caesar” and “Antony and Cleopatra” to run in repertory, with Patrick Page playing Mark Antony in both shows. Page withdrew before production began due to a conflict; company stalwart Andrew Long was tapped just before rehearsals. Weeks into the run, mere minutes into a performance of “Caesar,” running up the vast staircase on the set, Long badly injured his foot.

Enter Kurt Rhoads. Immediately.

Rhoads, Long’s understudy, was braced. The company had canceled performances of “Tamburlaine” earlier that season when star Avery Brooks was injured and his understudy was unavailable due to a family emergency. “I knew I should be ready,” Rhoads says from New York. The performance went off without a hitch or even an announcement about the early change, and Rhoads finished the remaining weeks of the run.

The actor ventures a football analogy of being brought on in the clutch: “You’re kind of like the kicker. No one wants to disturb your concentration.”

Meisle says, “You really don’t have any time to get scared or make it about yourself. It’s fast and furious. You have to jump in with both feet — broken or not.” The “Much Ado” production not only featured a fountain that Meisle had to plunge into (”They didn’t tell me about that right away,” she says with a charming laugh), but it also called for a fair amount of salsa dancing. Meisle, who was also enduring an IRS audit at the time, remembers thinking, “Are you serious?”

With “Necessary Sacrifices,” director Jennifer Nelson says there were “24 to 48 hours of panic” when Toney — who had been acting as Don Pedro in “All’s Well” while rehearsing “Necessary Sacrifices” — couldn’t go on. Luckily, Nelson and Wallace had worked fast before, doing August Wilson dramas on a compressed schedule for summer stock. The crash course at Ford’s included brief intensive director-actor sessions drilling down on character and play, and Nelson says co-star David Selby, who played Lincoln in “The Heavens Are Hung in Black” at Ford’s, offered himself for extra sessions with Wallace running lines.

For Wallace, the process has been a mind-bending reversal of the norm: He was air-dropped into a show where the costumes, set and lights were ready to go while he was still learning his lines. Wallace kept his script for the initial performances last week, with Nelson and others making curtain speeches to explain the circumstances to patrons.

“It’s not like the script is glued to my face,” Wallace clarified on Jan. 27.“I have it in case I get into trouble.”

He aims to be off-book Sunday, a deadline that’s self-imposed. “They know,” Wallace says of the Ford’s team. “It’s a lot of words. I can only put so much in my head every day.” Can an actor get any sleep under this kind of pressure? “Yes,” Wallace reports. “Because I’m dog tired.”

“There’s nothing like it,” Meisle says of being hired to bridge a sudden gap. “And you do feel a little bit like a hero.”

“When called upon to do something herculean,” Kahn says of actors, “they usually can.”

But Meisle adds, “When you’re in a company and you see someone replaced, it’s interesting to watch the young people go, ‘Oh, wow.’ Just because you get the job doesn’t mean it’s secure. It’s a real lesson.”

Necessary Sacrifices

through Feb. 18. Tickets $20 to $60. Ford’s Theatre, 511 10th St. NW. 202-347-4833. www.fordstheatre.org.