About a century ago, a comic strip called “Little Orphan Annie” began its decades-long run in newspapers.

It was followed by radio programs, movies, and eventually a massively successful Broadway musical that has (thus far) spawned a trio of film adaptations of its own.

All of this to say that one little red-headed girl has been a pop culture juggernaut for better than 100 years.

And the Benedum Center in Downtown Pittsburgh filled up on Friday’s opening night with theatergoers to see “Annie” — some maybe for the first time, and some maybe for the hundredth.

And while the show can feel a little stale to those of us who’ve known it since childhood, it’s still a wholesome smile-maker of a musical with great tunes and real heart.

“Annie” debuted on Broadway in 1977 and ran for six years — a jaw-dropping run at the time.

It won seven Tony Awards, including the one for Best Musical, and features a book by Thomas Meehan, music by Charles Strouse and lyrics by Martin Charnin.

The most popular film adaptation was released in 1982 and starred marquee names of stage and screen including Carol Burnett, Tim Curry and Bernadette Peters.

And putting aside those frustratingly catchy songs (I will be singing “Tomorrow” under my breath for the rest of the weekend), there is a gripping plot to “Annie.”

The musical opens on a dingy New York City orphanage in 1933, 11-year-old Annie (Hazel Vogel) tells her fellow orphans about her parents, who left her when she was a baby along with a locket and a note that they would come back for her someday. Annie tries to run away, drawing the ire of the orphanage’s cruel (and tipsy) manager, Miss Hannigan (Stefanie Londino).

Grace Farrell (Julia Nicole Hunter), the secretary for billionaire Oliver Warbucks (Christopher Swan), appears at the orphanage to find a child to spend Christmas at the Warbucks mansion.

She selects Annie to come along — and Warbucks is quickly charmed by the young girl. He decides that he’d like to adopt her, but Annie balks, holding out hope for her biological parents. So Warbucks uses his incredible resources to hunt for Annie’s mother and father, offering a large monetary reward.

In the meantime, Miss Hannigan’s con brother Rooster (Rhett Guter) and his girlfriend, Lily St. Regis (Isabella De Souza Moore) show up and decide to use Miss Hannigan’s knowledge of Annie to convince Warbucks that they’re Annie’s parents and collect the cash.

Along the way, Annie meets an adorable dog named Sandy (according to the program, his real name is Kevin and he got some of the biggest cheers of the night), visits a Great Depression-era “Hooverville” camp, lives it up in NYC and — in a “Forrest Gump”-esque scene — uses the power of a beautifully-belted song to convince FDR’s cabinet to devise the New Deal.

Vogel is extremely winning, portraying the scrappy-but-sweet character of Annie with tireless optimism throughout the two-and-a-half-hour performance. Her voice has a ton of power behind it already at such a young age.

She and Swan play off of each other nicely, both in comedic and heartwarming moments. Swan, himself, exudes an old-fashioned star power and command that fits Warbucks perfectly, and as opposed to Albert Finney’s stormy and forbidding beginnings in the 1982 film, he warms up to Annie almost immediately.

Londino looked like she was having a ton of fun as Miss Hannigan, playing the character as an effortlessly hilarious blend of Carol Burnett and Jane Lynch (with a few shots of whiskey thrown in). She was hilarious and did some terrific drunk acting — not an easy feat. Guter and De Souza Moore are both charming chameleons, as well, and join her in showstopping Act 1 number “Easy Street.”

Hunter is lovely and graceful as Grace Farrell, as well. And the entire ensemble — especially the cast of kids — puts their all into the production.

The musical is more invested in history and politics than many might remember, set against the backdrop of the Great Depression and sharply contrasting the rich and poor characters and settings.

The visual elements of this production are instrumental here; scenic design (by Wilson Chin) and lighting (based on design by Philip S. Rosenberg) are dingy, neutral and dim in the scenes at the orphanage but bright, colorful and crisp in the Warbucks manse.

Costume designer Alejo Vietti worked in these dual sides as well, taking Annie from the ill-fitting greige uniform of the orphanage to bright blue, seafoam green and crimson dresses after she’s received a gussied-up wardrobe. All of the period costumes are a lot of fun, from Warbucks’ well-tailored suits to the sumptuous glittering gowns and stylish frocks worn by the female characters.

Director Jenn Thompson kept the heart of this large-scale, classic show beating with every beat, and choreographer Patricia Wilcox made all the right moves, doing an especially stellar job with the kids’ scenes (“You’re Never Fully Dressed Without A Smile” brought the house down in the second act). And the orchestra pulled off every note flawlessly, under the music direction of Andrew David Sotomayor.

Now that the Pittsburgh weather has warmed up, it’s a good time to walk around singing “the sun will come out tomorrow.” “Annie” may be a well-worn favorite, but it’s still a good time for all ages.

“Annie” will have performances at 2 and 7:30 p.m. on Saturday, March 15 at the Benedum Center in downtown Pittsburgh. For tickets, visit trustarts.org.