All of Hollywood's greatest stars had to start somewhere, right? Usually, that meant small roles in some of our favorite sitcoms. Find out where you've definitely seen some of the world's most popular celebrities before they were ever famous.
Jessica Alba in "The Secret World of Alex Mack"
Remember this iconic '90s show? "The Secret World of Alex Mack" was about a teenage girl with hidden superpowers, and Jessica Alba played Alex's crush's girlfriend. Her character's name was also Jessica, and she was featured in three episodes total.
Mila Kunis in "7th Heaven"
So many people have guested on "7th Heaven," Mila Kunis included. It was her first television role before she was cast as Jackie on "That '70s Show." She played Ashley, a bully who eventually befriends Lucy and stirs the pot for the family.
Leighton Meester in "7th Heaven"
Before she was ever Blair Waldorf, the role that she's best known for, Meester had a small role in season eight of "7th Heaven." She played a tutor named Kendall who def inspired her mean girl character on "Gossip Girl."
Adam Scott in "Boy Meets World"
Looks like Paul Rudd taught Adam Scott a thing or two about aging like a fine wine because this photo is from a 1995 episode of "Boy Meets World." He played Gifffin Hawkins, a member of a band as well as a self-proclaimed tough guy at John Adams High School.
Millie Bobby Brown in "Grey's Anatomy"
Before Eleven, she was Ruby, a patient at Seattle Grace Hospital. Her mother fell and hit her head, and Dr. Owen Hunt helped walk her through a procedure over the phone until help could arrive.
Bradley Cooper in "Sex and the City"
Bradley Cooper's first credited role was in the hit HBO show, "Sex and the City." He plays a jerk — shocker — that Carrie meets on a night out. They don't hit it off, and he didn't return for another episode. It served as a great launch point for his career, though.
Gabrielle Union in "7th Heaven"
From "10 Things I Hate About You" to "Bring It On," Gabrielle Union has quite an impressive filmography. She guested on "7th Heaven," and played Mary's friend Keesha Hamilton in season one. She lasted for five episodes before moving on to bigger and better roles.
Leonardo DiCaprio in "Growing Pains"
Before "Titanic," there was "Growing Pains." Leo was featured in the show's final season as Luke Bower, a homeless teen who ended up staying with the Seaver family. He was adorable even way back then!
Ryan Gosling in "Are You Afraid of the Dark?"
Ryan Gosling, the heartthrob from "The Notebook," got his start on "The Mickey Mouse Club" with Britney Spears and Justin Timberlake. But for those who can't remember that far back, he was also in the spooky film, "Are You Afraid of the Dark?" as Jamie Leary, the brother of the boy who was death-obsessed.
Milo Ventimiglia in "The Fresh Prince Of Bel-Air"
You know Milo best from "Gilmore Girls" and This Is Us," but did you know he was on one episode of "The Fresh Prince of Bel-Air"? He played a partygoer at Will's house and even had a couple of lines. That was his first television role!
Matthew McConaughey in "Unsolved Mysteries"
McConaughey's debut role was in one episode of "Unsolved Mysteries" way back in the day. Before he was ever dazed and confused, he played an ex-marine and young father who meets a tragic end.
Alex Borstein in "Friends"
Alex Borstein is best known for her role in "The Marvelous Mrs. Maisel" and her small part in "Gilmore Girls." But did you recall her on that one episode of "Friends"? She performs a one-woman show at Joey's soap opera party.
Ellen Pompeo in "Friends"
Before "Grey's Anatomy" dominated our streaming services, Ellen Pompeo guest-starred on "Friends" as Ross and Chandler's college crush. She appeared in the show's final season, and the episode was something of a train wreck.
Lucy Liu in "Beverly Hills, 90210"
Lucy Liu had the quickest role in Aaron Spelling's hit sitcom. She played Courtney, a straight-A student who took Brad's place at the top. She was only featured on one episode, though.
Craig Robinson in "Friends"
No, this isn't Robinson in his role as Darryl from "The Office." He did, however, play a store clerk in the final season of "Friends" before he was cast as the warehouse manager at our favorite paper supply chain.
Keri Russell in "Boy Meets World"
Keri Russell, best known for playing the title character in "Felicity," was featured very briefly on another sitcom, "Boy Meets World." She played Mr. Feeney's niece who briefly hooks up with Eric.
Michelle Williams in "Home Improvement"
Though Michelle Williams is best known for her lead role on a different sitcom, "Dawson's Creek," she also had a brief role on Tim Allen's "Home Improvement." she played Brad Taylor's girlfriend, Jessica.
Neil Patrick Harris in "Blossom"
Neil Patrick Harris, now a hugely famous performer and actor, was featured in the hit '90s show "Blossom" for one episode. He played Derek Slade, one of his first of many suave and charming roles. That episode also featured Tori Spelling!
Vivica A. Fox in "The Fresh Prince of Bel-Air"
Vivica A. Fox played Jazz's sister Janet in one season of Will Smith's hit show. She goes on a date with Will, but the sparks do not fly. Then, she gets set up with Carlton, and the two actually kind of click.
Hilary Swank in "Beverly Hills: 90210"
Hilary Swank had a slew of small roles before her big break in "Boys Don't Cry." She had a slot on "Growing Pains" and "Evening Shade." Later, she nabbed a regular role in "Beverly Hills: 90210," playing Zach's mom Carly Reynolds.
Cole Sprouse in "Friends"
Cole Sprouse played Ross's lovable son Ben on "Friends." He was in a few episodes early in the show and won over the hearts of casting directors everywhere. He then went on to star in "The Suite Life of Zack and Cody" with his brother Dylan.
Don Cheadle in "The Fresh Prince of Bel-Air"
Don Cheadle's role as Ice Tray in "The Fresh Prince of Bel-Air" was so impactful that writers nearly gave him a spin-off series. Though that didn't happen, Cheadle's career thankfully took off shortly after and he landed several major movie roles.
Kat Dennings in "Sex and the City"
Kat Dennings played 13-year-old Jenny Brier during one episode of SATC. She was a spoiled teen who hired Samantha for her PR expertise while planning a lavish bat mitzvah. Since then she's had television shows written around her.
Marla Sokoloff in "Full House"
Sokoloff played Gia, Stephanie's cool girl friend in high school who encouraged all sorts of bad behavior in the Tanner house. Since then, she landed roles in "Boy Meets World," "Home Improvement," "Step By Step," and "3rd Rock From the Sun."
James Marsden in "The Nanny"
One of Marsden's earliest roles was as Eddie in "The Nanny." He was Margaret Sheffield's boyfriend for a few episodes. After that, he landed roles in "Saved By The Bell: The New Class" and "Party of Five."
Mena Suvari in "Boy Meets World"
Best known for "American Beauty," Mena Suvari had not one, but two quick roles on "Boy Meets World," where she played different characters. The writers thought no one would notice. First, she played a nonessential girl named Laura, and then she played Hilary, a girl at a party that Cory attends, sans Topanga.
Anne Hathaway in "Get Real"
Anne Hathaway starred in this one-off sitcom called "Get Real." It was about a family from San Francisco. Spot that other familiar face? It's none other than Jesse Eisenberg.
Reese Witherspoon in "Friends"
Reese played Jill Green, Rachel's sister, when she guested on "Friends." One of her more notable episodes was when she babysits Rachel and Ross's daughter, Emma, and she returns her with newly pierced ears. Yikes!
Britney Spears in "How I Met Your Mother"
Britney Spears has been featured in tons of celebrity guest-starring roles throughout her career. She once had a two-episode gig on "How I Met Your Mother" where she played a receptionist who fell in love with Ted, but then wound up engaged to Barney. She also has earned roles on "Glee," "Jane the Virgin," and "Sabrina the Teenage Witch."
Tessa Thompson in "Grey's Anatomy"
Tessa Thompson played the Chief of Surgery's niece, Camille Webber. She's first seen during the prom episode when she's diagnosed with ovarian cancer. In season four, her role was replaced by Camille Winbush.
Kesha in "Jane the Virgin"
Pop star Kesha played Jane's rude musician neighbor who won't turn her speakers down. Jane has trouble getting newborn Mateo to sleep, and the racket doesn't help. The two solve that problem in a convoluted, sitcom-type way.
Pete Wentz in "One Tree Hill"
"One Tree Hill" hosted two Fall Out Boy performances during its time on the air. Wentz then starts seeing Peyton, and he joins her girls' weekend trip to connect with her. However, the episode ends with her reconciling with an ex.
Michelle Obama in "iCarly"
The former First Lady herself made an appearance on the hit Nickelodeon show, "iCarly." She was there to promote President Obama's "Joining Forces" initiative, which was created to support military families missing their loved ones.
Serena Williams in "Law and Order: SVU"
The tennis star had a quick role alongside Mariska Hargitay when she guested on "SVU." She played a basketball player who accidentally became the victim of an Internet porn scandal when she took her top off at a bar and was photographed without her knowledge.
Prince in "New Girl"
Prince was initially offered a cameo on the second season of "New Girl," but turned it down. His manager was a fan of the show and found a way to insist he reconsider, so the writers wrote an entirely new episode around his appearance.
Paris Hilton in "Supernatural"
Paris Hilton played a brief role as a Leshi, a shape-shifting creature. It learned how to shapeshift into none other than the socialite, Paris Hilton herself.
Carrie Fisher in "The Big Bang Theory"
Sheldon and none other than James Early Jones made the mistake of knocking on Carrie Fisher's door in one episode of "The Big Bang Theory." She answered with a bat and said, "It's not funny anymore, James." Turns out, that was the first time the former "Star Wars" co-stars ever met in real life.
Mark Hamill in "The Big Bang Theory"
But where there's Carrie Fisher, Mark Hamill isn't far behind. This "Star Wars" star also had a brief cameo on "The Big Bang Theory." In season 11, he officiated Amy and Sheldon's wedding.
Dwayne Johnson in "Hannah Montana"
In one episode of "Hannah Montana," Miley and Lilly posed as hotel aestheticians and gave the action star a full makeover so they could take an embarrassing photo of him so the paparazzi wouldn't expose her as Hannah Montana.
Kris Jenner in "The Mindy Project"
Mindy managed to book the Kardashian matriarch for an episode of her show. Jenner was doing a book signing when Mindy rushes to the front of the line in order to ask Jenner to promote her fertility clinic.
Jon Hamm in "Gilmore Girls"
Though he's a total stud on "Mad Men," Jon Hamm takes the "Gilmore Girls" star on a really, really bad date. Lorelai says he has "zero personality" but did know too much about his Jaguar and his favorite wine. Yawn.
Oprah Winfrey in "30 Rock"
On a hilarious episode of "30 Rock," Tina Fey's character Liz Lemon has a conversation with none other than Oprah Winfrey while on a plane. Turns out, the whole encounter was a hallucination, but Winfrey really did show up to act!
Brad Pitt in "Friends"
Brad Pitt appeared on "Friends" while he was still married to Jennifer Aniston. Funnily enough, his character was the president of the "I Hate Rachel Green Club" in high school.
Cher in "Will & Grace"
Cher has appeared on "Will & Grace" twice because of Jack's infatuation with her. The first time, Jack thinks she's a Cher impersonator. And the second time consists of a musical number in one of their dream sequences.
Genuwine in "Parks and Recreation"
Genuwine was one of the special guests who appeared at the Pawnee/Eagleton Unity Concert hosted by the Pawnee Parks Department. What a strange choice this was.
Charlize Theron in "Arrested Development"
Theron actually had an Academy Award under her belt before she appeared on this comedy show. She played Rita, a woman who was briefly dating Michael. However, she was thought to be a spy because of her accent.
Ed Sheeran in "Game of Thrones"
Ed Sheeran showed up for "Game of Thrones" season seven premiere. He played a Lannister soldier who actually sang around a fire. He loved the role, but got some backlash from it and actually ended up deleting his Twitter because of it. It was a little cheesy, you have to admit.
Mario Lopez in "Golden Girls"
Mario Lopez played Dorothy's student, and he won an essay contest with a paper he wrote about why he loved living in America. Unfortunately, Lopez's character was an illegal immigrant, and actually got deported. Dorothy tried to contest the claims, but failed.
Demi Lovato in "Grey's Anatomy"
Singer Demi Lovato played a girl with a bizarre neurological disorder that allowed her to hear every single noise inside of her body. She was misdiagnosed with paranoid schizophrenia, but thanks to McDreamy, she was able to get help and treatment for the correct problem.
Owen Wilson in "Community"
Owen Wilson didn't tell anyone that he was going to guest star on one episode of "Community." He played a member of the "cool" study group in the first season, and tries to claim Joel McHale's table. It doesn't work.
Carole King in "Gilmore Girls"
Did you know Carole King wrote that iconic theme song? "Where You Lead" is one of her hits, and it served as the show's theme for seven years. She made an appearance in the show's second season as music store owner Sophie Bloom.
Bruce Willis in "Roseanne"
No one — not even Roseanne Barr — knew that Bruce Willis was going to pull this stunt on the "Roseanne" set. At the end of filming an episode, the "Die Hard" star just walked onto the set and got into bed beside Barr. For what? For comedy.
Victoria Beckham in "Ugly Betty"
Posh showed up for an episode of "Ugly Betty" to play Wilhelmina's snooty maid of honor in her wedding. Talk about the style of the times. That tan and that outfit are majorly clashing.
Kevin Hart in "Modern Family"
Kevin Hart appeared in season three of "Modern Family" as the Dunphy's neighbor, Andrew, an orthopedic surgeon. He makes two appearances, once when offering to help Phil build a treehouse, and again when he somehow convinces Phil to buy a Porsche.
Snoop Dogg in "One Life to Live"
Snoop is more of a pop culture icon and less of an actor. He cameoed on the canceled ABC soap opera "One Life to Live" where he sang his own version of the show's theme song. He'd been a fan of soaps ever since he was a child.
Joe Manganiello in "The Big Bang Theory"
The "True Blood" actor was featured on "The Big Bang Theory" as a huge fan of the game Dungeons and Dragons. He actually hosts games in his basement in real life and has other celebs like Taran Killam over to play.
George Clooney in "Roseanne"
George Clooney had a memorable role as Jack and Roseanne's original boss, Booker Brooks. He worked at Wellman Plastics and started dating Jackie, but the relationship didn't last very long.
George Clooney in "Golden Girls"
Clooney also had a quick role as a detective in "Golden Girls." Detective Bobby Hopkins stays with the ladies while trying to catch a jewel thief who moved in across the street. Unfortunately, he gets shot in the process and sort of overstays his welcome.
Rita Moreno in "Grey's Anatomy"
The "West Side Story" star plays the estranged wife of a memory loss patient in the show's twelfth season. Right now, she's on the show "One Day at a Time."
Krysten Ritter in "Gilmore Girls"
Before she was Jessica Jones, Ritter had a brief role in the seventh season of "Gilmore Girls" as one of Rory's college classmates. She encouraged Rory to loosen up a little, but the friendship didn't last long when Ritter's character found out Rory had lied to her about her boyfriend drama.