You only get one chance to make a first impression, and actors typically have little say in what that chance is.

Early in their careers, actors are near the bottom of Hollywood’s power structure, which is why the first credits of most of our biggest stars seem unworthy of the talents they will become. Tom Hanks debuted in the shocker “He Knows You’re Alone,” and he wasn’t the “He.” Viola Davis didn’t even get a name as “Nurse” in “The Substance of Fire.” And Jennifer Lopez is at the end of the cast list of the forgotten “My Little Girl.”

So the people who wow us their first time out are unicorns, who luck into a great role and nail it. That can happen in several ways. Specific requirements can match a specific role, like Minneapolis’ Barkhad Abdi as a pirate in “Captain Phillips.” Achieving fame in other media can help a new actor skip “Rejected Suitor No. 2” parts, like Dwayne Johnson did in “The Mummy Returns,” Diana Ross in “Lady Sings the Blues” and David Bowie in “The Man Who Fell to Earth.” A prominent stage career helped Emma Thompson in “The Tall Guy” and Julie Harris in “The Member of the Wedding.”

Dana Hill’s heartbreaking performance in “Shoot the Moon” would be on this list if it didn’t feel unfair to include someone whose first movie was preceded by a ton of TV credits, but Hill represents another category of memorable debuts: kids. Unknown children often get flashy roles — think of Reese Witherspoon in “The Man in the Moon,” Tatum O’Neal in “Paper Moon,” Anna Paquin in “The Piano” — and give some of the most believable performances.

That many of them fail to follow up splashy debuts may say something about the depth of their bond with their first directors, or maybe they never found another role that suited them so perfectly.

I’m not sure these seven performances are the best first times of all time, partly because it’s hard to gauge the impact of debuts before I was watching movies (folks say Lauren Bacall blew audiences away in “To Have and Have Not,” but I wasn’t around). Still, these actors made first impressions that, for me, last.

Barbra Streisand, ‘Funny Girl’ (1968)

What’s more frustrating: that she has made so few movies since her Oscar-winning debut or that she’s never been as good again? You could argue years of playing Fanny Brice in the stage “Funny Girl” gave Streisand a boost, but it probably made it harder to seem natural and unrehearsed in the movie. No actor has ever emerged as fully formed, as original and with such unique timing as Streisand does here, gracefully blending romantic lead with outrageous clown, Broadway belter and heartbreaking tragedian.

Keisha Castle-Hughes, ‘Whale Rider’ (2002)

Only two children have been nominated for the best actress Oscar and both were nonactors: Quvenzhané Wallis in “Beasts of the Southern Wild” and this Aussie. Castle-Hughes got the nod because of a jaw-dropping speech she gives to convince her Maori tribe she should be allowed to lead them even though she’s a girl. It’s spine-tingling to watch Castle-Hughes do opposing things at once in that big scene: sob with pent-up emotion while fighting to subdue her tears.

LaKeith Stanfield, ‘Short Term 12’ (2013)

The tender drama’s cast was filled with unknowns, but two have already gone on to win Oscars: Brie Larson (“Room”) and Rami Malek (“Bohemian Rhapsody”). Obviously, director Destin Daniel Cretton is an ace talent spotter and his biggest discovery could be Stanfield, who later impressed as a latter-day slave in “Get Out” and a detective in last year’s “Knives Out.” Stanfield is deeply moving as a kid who grew up in a group home and, afraid to leave, expresses his fears in a song called “Life’s Like,” which Stanfield co-wrote.

Julie Andrews, ‘Mary Poppins’ (1965)

Like Streisand, Andrews came to the movies after a robust career on stage. Andrews began as a “girl singer” in English music halls, transitioned to Broadway and debuted, at 30, with an Oscar-winning, practically-perfect-in-every-way performance in this children’s classic. Making her work even more noteworthy are a bunch of degrees of difficulty: She had to act opposite animated characters. She knew the creator of her character didn’t want the movie to be made. She sang. And she acted opposite kids.

Alan Rickman, ‘Die Hard’ (1988)

The Englishman already had tons of stage and TV credits, but the first time he brought his plummy voice to the movies, he created one of the most elegantly vile terrorists of all time. Rickman would go on to shine in “Truly Madly Deeply” and “Sense and Sensibility,” but he was never better than in some people’s favorite Christmas movie. Our unfamiliarity with him suits the thriller because it keeps us guessing about his motives and, for longer than we should, has us hoping he’s not the bad guy he so clearly is.

Timothy Hutton, ‘Ordinary People’ (1980)

It’s no surprise when an actor who becomes a director has a deft touch with performers, but “Ordinary People” is one of the best-cast movies of all time, whether it’s one-scene actors such as Dinah Manoff and Fredric Lehne or the five leads, all of whom flourished under Robert Redford. Hutton, as a jittery survivor of a suicide attempt, keeps his emotions so close to the surface that he seems practically naked, especially opposite Judd Hirsch as his therapist. Like many a young actor who found the perfect first role, Hutton — who won an Oscar — has never come close since.

Lupita Nyong’o, ‘12 Years a Slave’ (2013)

Even better than a unicorn who dazzles us with a debut performance is someone who has the talent, and opportunity, to continue to impress. Nyong’o won her Oscar for Steve McQueen’s calmly horrifying drama, likely impressing voters with the scene in which her character, who is enslaved, asks a friend to kill her, but her dual performances in “Us” are even more extraordinary.