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They've been memed and lampooned — and now they're some of Netflix's most talked about films.

"Bird Box," Netflix's sci-fi horror film based on a book of the same name, and "Bandersnatch," the "Black Mirror" series' choose-your-own-adventure film, emerged as cultural touchstones at the end of 2018, helping the streaming service show that it could soon duplicate its success with original series with original movies.

"Bird Box," which began streaming on Dec. 21, follows Malorie, a mother navigating a world in which people who see a mysterious entity are driven to suicide. In order to avoid whatever is driving people to madness, the characters in the film blindfold themselves as they move around the outside world.

Netflix tweeted on Friday that within days of its release, the film had been streamed by more than 45 million accounts — the best opening week for an original movie produced by the platform.

"This is just one more drop in the bucket that announces to American entertainment audiences that Netflix is no longer optional," said Robert Thompson, professor of television and pop culture at Syracuse University.

Thompson said that "Bird Box" has done for Netflix films what "Orange Is the New Black" and "House of Cards" did for its original television series, helping it move beyond licensing the content of other companies.

Netflix has released dozens of original movies dating to 2015's "Beasts of No Nation," but its films have come and gone without registering a fraction of the attention of "Bird Box."

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"This is by no means Netflix's first movie ... but this one has really penetrated cultural consciousness," Thompson said.

Adding to Netflix’s movie lineup is “Roma,” a semi-autobiographical look at the life of its director, Academy Award-winner Alfonso Cuarón, set in Mexico City in the early 1970s. The film has received award buzz, and has been nominated for three Golden Globes, including best director and best foreign language film.

Netflix's movie buzz comes as the company faces growing skepticism over whether it can maintain the success that in recent years has made it one of the world's most valuable entertainment companies. Other major media players, including Disney and AT&T's WarnerMedia, are preparing to launch rival streaming services, and Netflix may soon have to rely on its original movies and series as other companies hold back their content.

Although he's skeptical about Netflix's numbers, saying that an independent agency hasn't vetted them, Thompson said the convenience of streaming services allows for more people to engage with the film, leading it to grow in popularity.

But why this particular film has gone viral is anyone's guess, he said.

"Compared to all the great stuff that has come out on streaming services over the last several years, I'm not sure I'd say this is the most compelling," Thompson said. "It’s a combination of when it came out, what else was going on in media environment, and the mysterious showbiz process when something goes viral."

As the movie entered cult status, thousands of users on Twitter and the short-form video app TikTok began posting recordings of themselves doing the "Bird Box Challenge" — blindfolding themselves as they either re-enact scenes from the film or try to move around their homes, and occasionally the outside world, just like characters in the film.

Y’all gotta chill #BirdBoxChallenge why he do the baby like that pic.twitter.com/hspFdNHzTC — Mya (@sosomyaaa) December 27, 2018

When the Dog has to go out, but you wanna make sure he doesn’t get caught lackin and run out in front of a car or something #BirdBoxChallenge #Birdbox pic.twitter.com/Yn0WjSNrm7 — Wes Finesse 𓅓 (@rwharris95) December 26, 2018

Some videos include blindfolded parents leading their blindfolded children around like Bullock's character does throughout the movie. Others have blindfolded their pets — a tactic not included in the film.

On Wednesday, Netflix implored those who watched "Bird Box" not to hurt themselves while taking part in the challenge.

"We don’t know how this started, and we appreciate the love, but Boy and Girl have just one wish for 2019 and it is that you not end up in the hospital due to memes," Netflix tweeted, referring to two of the film's characters.

"Bird Box" wasn't Netflix's only sci-fi hit over the holidays. On Dec. 28, the company released "Bandersnatch," a movie that is part of the "Black Mirror" series and that asks users to make choices throughout the film.

While "Bandersnatch" has also received significant internet buzz, it hasn't quite become the sensation of "Bird Box."

i’ve been watching bandersnatch for 3 hours now pic.twitter.com/Kuyzo36Caa — leslie bonner (@lesjbonner) January 2, 2019

me choosing the cereal in Bandersnatch pic.twitter.com/4cPv0KMBFs — mari ️ (@maricruzponce17) January 2, 2019

When someone starts to talk to me about Bandersnatch #AM2DM pic.twitter.com/NiBxBla5we — Rebecca (@rbccbsdl) January 2, 2019

"Bandersnatch" follows game programmer Stefan Butler as he attempts to deliver a game of the same name in time for Christmas 1984. As the viewer makes choices for Stefan, the character devolves into a deep depression and increasing paranoia. The choices lead to a number of different endings.

"Bandersnatch" rated slightly higher among critics than "Bird Box" — it received 68 percent on Rotten Tomatoes, compared to 65 percent for "Bird Box" — and although it hasn't received the cult following that the Sandra Bullock vehicle has, it has still been relentlessly memed online.

"2018 was a big year for this genre across the board. But they're excelling and one of — if not the — major players in it," Thompson said of Netflix's sci-fi offerings.