Ratajkowski first appeared on season 3 in 2009 and in a follow-up episode later in the season in 2010 as a character named Tasha.

In February of 2023, the model and actress posted a throwback clip from the guest spot she did as a teenager, and reminisced about her time on set.

"I was 16 or 17 and took two weeks off school to shoot two episodes," she shared in the video posted to TikTok, which featured footage from the appearances.

At the end of the clip, a teenage Ratajkowski comes into the frame and interacts with the characters Gibby, played by Noah Munck, and Sam, who was portrayed by Jennette McCurdy.

"Gibby, my first love lol," the star then wrote, also noting, "I met Jennette McCurdy and her mom."

Before Butler was an Oscar-nominated movie star, he had roles on numerous kids' shows including Zoey 101, Hannah Montana and iCarly.

In 2007, the Elvis actor appeared on season 1 of the Nickelodeon show as Jake in an episode aptly called "iLike Jake."

Prior to Harry Styles, Niall Horan, Louis Tomlinson, Zayn Malik and Liam Payne going their separate ways, the boys of One Direction appeared on the Nickelodeon show as themselves after accepting an invitation to perform on the fictitious web series the show is based around.

Former First Lady Michelle Obama also got in on the fun, when she guest-starred on the show as herself on an episode entitled "iMeet the First Lady."

After landing roles in films like Superbad, Easy A and The Help, Stone made a fun guest appearance on the series in 2012 as a super-fan of the web series.

During Parsons' tenure as Sheldon Cooper on Big Bang Theory, he made a quick stop on iCarly on season 5's "iLost My Mind."

Before Justice went on to have her own Nickelodeon show, Victorious, she appeared as boxing phenom Shelby Marx on an episode of iCarly.

A former child star, SNL's Thompson appeared as himself in the 2011 Victorious/iCarly crossover, iParty with Victorious.

Thompson's former SNL castmate, Killam, also made an appearance on the Nickelodeon show before he landed the Saturday night gig. On "iMet the First Lady," Killam played one of Michelle Obama's Secret Service agents.

Fey and Fallon appeared on one of the series' final episodes, in which the Tonight Show host invited the iCarly kids to appear on his show.

After starring together in 2003's School of Rock, Black reunited with Miranda Cosgrove, who plays Carly, on an episode called, "iStar a Fan War."

Before Shum Jr. danced his way around McKinley High School on Glee or scrubbed in on Grey's Anatomy, he appeared on the iCarly TV movie, iGo to Japan.

The American Idol runner-up appeared on an episode entitled "iRocked the Vote," in which he competed, as himself, in a fictitious competition show called America Sings.

The Always Be My Maybe actor appeared in an early episode of the series as a teacher at the kids' high school, in an episode entitled "iGot Detention."

Before starring in films like Teen Beach Movie and To All The Boys: P.S. I Still Love You, one of Fisher's first credits ever was on an episode of iCarly called "iSpeed Date."

Also appearing in "iSpeed Date" was soon-to-be Glee star Overstreet.

Speaking of Glee, Sue Sylvester herself appeared on an episode of iCarly as Pam Puckett, Sam's mom.

Back in season 1, the "Hey There Delilah" singers appeared on the show to perform on the webcast as a favor to Carly's brother, Spencer, after he saved frontman Tom Higgenson's life.

Good Charlotte also appeared on the series, when they performed in the iGo to Japan TV movie.