THEN AND NOW: The 'Avengers' stars before they were famous

The movie was written and directed by his father. Downey was five years old when the movie was released, and played a puppy.

Downey went on to star in movies like "Hail Cesar," "Home for the Holidays," "The Shaggy Dog," and "Gothika."

He made his first appearance as "Iron Man" in 2008, and his character has had three total standalone films. With the introduction of Tom Holland's Spider-Man, Tony also took on the role of a mentor to the teen web-slinger.

When he was younger, Ruffalo was a bartender, navigated Los Angeles with a motorcycle, and participated in theater productions.

He also starred in movies like "13 Going on 30" and "Collateral."

In recent years, Ruffalo has been nominated for Golden Globes and Oscars. He has also won two SAG awards.

She also starred in the 2003 movie "Girl With a Pearl Earring" and the 2004 movie "The Perfect Score" (alongside future "Avengers" costar Chris Evans).

Acting aside, she also released albums back in the day.

Johansson also received a star on the Hollywood Walk of Fame in 2012, just one mark of her successful career. She'll star in a standalone Marvel film called "Black Widow," which hits theaters in May 2020.

He starred in comedies like "Not Another Teen Movie" and "The Perfect Score," but also starred in the 2004 thriller "Cellular" alongside Jason Statham.

And let's not forget that he played another superhero before starring as Steve Rogers/Captain America — Johnny Storm/Human Torch in the original "Fantastic Four" movies.

Evans' role as Cap has earned him several award nominations, especially at the Teen Choice Awards, Kids Choice Awards, and People's Choice Awards.

In 2018, Evans sported a moustache for his role as a police officer in the Broadway show "Lobby Hero" (which received a Tony Award nomination for best revival of a play).

He also starred in the 2019 Oscar-nominated film "Knives Out."

He went on to land roles on shows like "CSI: Crime Scene Investigation" and "Angel." Renner also portrayed real-life serial killer Jeffrey Dahmer in the 2002 movie "Dahmer."

It was his role as Staff Sergeant William James in 2008's "The Hurt Locker" that really put Renner on the radar of fans. Renner earned an Oscar nomination and a SAG Award nomination for the part. His role in Ben Affleck's "The Town" (2010) further added to his growing popularity, as he again landed Academy Award and SAG nominations, in addition to a Golden Globe nod.

His standout (and most heartbreaking) "Endgame" scenes took place in Vormir, when he and Black Widow argued over who should be sacrificed in order to retrieve the soul stone.

Next, Renner will star on his own show headed to Disney Plus, titled "Hawkeye."

He also had roles on shows like "The Golden Palace," "Picket Fences," and "ER." You might also remember Cheadle for his role as Basher Tarr in the "Ocean's" movies.

Based on an interview that has resurfaced, he's not a fan of costars who accidentally blurt out spoilers (like Ruffalo).

He also starred in "Million Dollar Baby," "The Hurt Locker" (with Jeremy Renner), and played Tupac Shakur in "Notorious."

Additionally, he's done various theater productions and was an understudy for "Avengers" costar Cheadle and "Westworld" star Jeffrey Wright.

Mackie starred in the movie "Detroit" and in "The Hate You Give" alongside "Riverdale's" KJ Apa, Regina Hall, and Common.

His first role ever was on the Australian soap opera "Neighbours." He was also on the Australian version of "Dancing With the Stars" in 2006. Watch him samba here.

Hemsworth was also in the 2018 drama "12 Strong." More recently, he starred in "Men in Black: International."

He'll reprise his role as the Marvel superhero in "Thor: Love and Thunder," scheduled for release on November 5, 2021.

"The Life and Adventures of Nicholas Nickleby" starred Anne Hathaway and Charlie Hunnam.

Hiddleston appeared in various UK TV series before making it big.

Hiddleston made his debut as Loki in 2011's "Thor." He also appeared in 2019's "Endgame" and is going to have his own series, which will be available on Disney's streaming service (Disney Plus). You can watch a teaser for the show here.

He went on to land roles on shows like "The Wire" and "The Office."

In 2012, Elba won a Golden Globe for his role in "Luther." He was also named People magazine's Sexiest Man Alive in 2018 and starred in the 2019 film adaptation of "Cats."

He was also in "Hot Tub Time Machine" and "Black Swan."

He also starred in the award-winning movie "I, Tonya" with Margot Robbie and Allison Janney. Stan and Mackie have their own show that will hit Disney Plus in 2020, titled "The Falcon and the Winter Soldier."

She is the younger sister of Mary-Kate and Ashley Olsen.

She also starred in "Ingrid Goes West" with Aubrey Plaza and "Wind River" with Jeremy Renner. Most recently, she appeared on "Sorry for Your Loss."

Before becoming Vision, Bettany started as Tony's A.I. system, Jarvis.

Bettany starred in the 2018 movie "Solo: A Star Wars Story."

He also played Stephen Hawking in a 2004 TV movie. Later, he became known for his role as Sherlock Holmes in "Sherlock."

He had the green stone, which allowed him to manipulate time and space.

In the UK, Holland played the titular character in the theater production of "Billy Elliot the Musical." Watch young Holland talk about the show without giving away too many spoilers here.

He made his debut as Peter Parker in "Captain America: Civil War."

He went on to land roles in popular shows like "The O.C." and "Parks and Recreation."

The first "Guardians of the Galaxy" was released in 2014. Pratt also starred in the "Jurassic World" movies.

She also had roles in "Crossroads," "Pirates of the Caribbean: The Curse of the Black Pearl," and "Avatar."

Saldana appeared in Drake's star-studded music video for "Nice for What."

One of her breakout roles was in the movie "Old Boy," which starred future "Avengers: Infinity War" cast members Josh Brolin, Elizabeth Olsen, and Samuel L. Jackson.

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Like costar Elizabeth Olsen, Klementieff was also in the 2017 movie "Ingrid Goes West."

Bautista and Dwayne "The Rock" Johnson competed against each other when they were wrestlers.

Bautista also starred in "Blade Runner 2049."

He's known for his roles in the "Fast and Furious" franchise, "xXx," and "The Chronicles of Riddick."

In "Infinity War," Groot preferred playing video games than helping with a mission.

Cooper went on to star in other TV shows, including "Alias" and "Kitchen Confidential."

Over the years, Cooper's various acting roles have earned him award nominations — from Oscars to Golden Globes. In 2014, he won a SAG award with the cast of "American Hustle." He also starred in and directed 2018's "A Star Is Born."

She was on the popular show for several years.

Like Gamora, she was an adopted daughter of Thanos.

He also had roles on "Law and Order," "ER," and "CSI: NY."

Boseman hosted "Saturday Night Live" in April 2018. He'll reprise his role as Black Panther in a sequel, set for release on May 6, 2022.

She was also on an episode of "Doctor Who."

We first met Shuri in "Black Panther."

She also had roles in "Restless City" and "All Eyez on Me."

Her first appearance in the MCU was in "Black Panther."

Before "Black Panther," he had roles on "Person of Interest," "The Messengers," and "Modern Family."

He was one of the most entertaining characters in "Black Panther."

He went on to land roles in "No Country for Old Men," "American Gangster," and "Men in Black 3."

Brolin also starred as Nathan Summers/Cable in "Deadpool 2."

He also went on to land starring roles in "The Chronicles of Narnia: Prince Caspian" and "Ice Age: Continental Drift."

Dinklage will also voice a character in the upcoming film "Angry Birds Movie 2."

He was in "Prometheus" and "Kick-Ass 2."

We first met his character in "Doctor Strange."

She was also in "Hook," "Sliding Doors," and "Shakespeare in Love" (which she won an Oscar for).

These days, Paltrow spends much of her time on her website, Goop. She also married Brad Falchuck in September 2018 and had a star-studded ceremony in the Hamptons.

He also starred in "Sin City" and "Traffic."

He's an Oscar-winning actor and starred in the "Sicario" sequel.

One of his early roles was in "Coming to America," in which he played a robber. He was also in "Jurassic Park," "Hail Cesar," "Goodfellas," and "Pulp Fiction."

Jackson also appeared in "Spider-Man: Far From Home."

Smulders is most-known for her role as Robin Scherbatsky on "How I Met Your Mother."

Aside from her MCU role, Smulders had roles in shows like "A Series of Unfortunate Events" and "Friends From College." In 2017, she made her Broadway debut in the comedy "Present Laughter." She was also in "Spider-Man: Far From Home."

The role wasn't her first in Hollywood, but it was one of her earliest. She also appeared on shows like "Hope & Faith" before starring in movies like "Scott Pilgrim vs. the World," "21 Jump Street," "Don Jon," and "Trainwreck."

Captain Marvel, who's arguably the strongest superhero in the MCU, helped rescue Tony and Nebula from space in "Endgame."

She played the character until the series finale aired in May 2010. Afterward, Lilly portrayed the bow and arrow wielding Tauriel in the "Hobbit" movies.

She first appeared in 2015's "Ant-Man."

She played Jackie Cook, the daughter of a famous baseball athlete.

She appeared in "Endgame" and is set to reprise her role as the warrior in "Thor: Love and Thunder."

She played a 12-year-old girl who was taken by an assassin. Portman went on to portray Padmé in the "Star Wars" movies. The actress also starred in "V for Vendetta," "Black Swan" (which earned her an Academy Award), and "No Strings Attached."

She'll return in the upcoming "Thor" sequel, playing a female version of the God of Thunder.

She went on to star in movies like "How Stella Got Her Groove Back," "Green Lantern," and "Olympus Has Fallen." Bassett also played Cate Banfield on "ER."

The character was first introduced in 2018's "Black Panther."

"Friends" fans might also recognize Favreau for his role as billionaire Pete Becker. He also played Foggy in the 2003 "Daredevil" movie.

He also starred in all the "Iron Man" sequels, "Endgame," and Tom Holland's "Spider-Man" movies.