LOS ANGELES >> You have a firm grip on this year’s Oscar nominees, last year’s winners and what host Jimmy Kimmel will undoubtedly joke about (and the best picture award goes to … oops).

But there are aspects of Hollywood’s stellar night that may be a surprise. Let’s pull the curtain back a bit on a ceremony that strives for effortless glamor but, like any machine, is made up of nuts and bolts and simple human need.

Besides stars, designer duds and lots of close-ups, here’s what else the 3 p.m. Sunday, March 4, telecast on ABC will include:

STAND-INS, AKA SIT-DOWNS

Cameras never find an empty seat at the Academy Awards, with a troop of seat-fillers at the ready to occupy any chair vacated by a bathroom- or bar-bound guest. A parade of extras in tuxedoes and gowns arrive hours before the show begins and are ready to swoop in and sit once the cameras start rolling.

Getting the gig, like so much in Hollywood, depends on who you know: Seat-fillers are family and friends of movie academy staff and accounting firm. Are there polite tussles to sub for Streep, Hanks or other A-listers, earning bragging rights? We can only hope.

STOMACH PAINS

Oscar guests are often hungry. It may be self-imposed, either because of nominee nerves or a skin-tight gown with no room for error or eating. Attendees do have a chance to nibble during a pre-show cocktail hour that includes hors d’oeuvres trays, but skip that and it’s three hours or more until a post-ceremony dinner at the Governors Ball.

Not all are invited, which means some famished guests end up asking their limo driver to head to fast food, fast. Advice from an insider: carry a clutch roomy enough for a ham sandwich and don’t fret that you’ll get busted by security.

STAY IN YOUR LANE

There are two paths on the Oscars red carpet: one for famous people, and one for everyone else. Stanchions and velvet ropes separate the recognizable from the not. Famous folks walk on the side of the carpet closest to the cameras and reporters, and stars often collide or share impromptu carpet greetings.

The non-famous, meanwhile, walk along the carpet closest to the fan bleachers, with beefy-looking security guards ushering them along to reduce star-gazing across the aisle. There’s everything to see, folks, but move along.

WRITERS, STAT!

Live shows inevitably hit speed bumps, such as last year’s supersized-one in which Warren Beatty and Faye Dunaway presented “La La Land” with the top trophy that belonged to “Moonlight.” Such gaffes and other standout moments become fodder for the host, with a village of comedy writers backstage to help craft witticisms.

The best, like Kimmel’s teasing rebuke to Beatty (“Warren, what did you do?!”) feel spontaneous and are out quickly so the audience doesn’t lose the thread.

Hosts also need to be ready with “savers” to follow a joke that bombs, says longtime awards writer Bruce Vilanch, who offers up an example: “That was about as funny as a screen door on a submarine.”

WINNERS, MEET MEDIA

Oscar recipients are shepherded backstage for photos and video and to face a rapid-fire Q&A session with a packed room of journalists (yes, “how does it feel to win” and “where will you keep your trophy” are staple queries).

While the winners clutch their award and, in some cases, a celebratory glass of booze, reporters hold up numbered cards to be called on by an academy representative. This has caused more than one star to exclaim they feel like they’re at an auction and playfully call out numbers. Reporters giggle.

With backstage monitors showing the ceremony, some winners ask to pause the questions to hear outcomes for nominated friends or colleagues. Reporters oblige.