20 Nickelodeon Celebrity Guest Stars You Probably Forgot About

Amy Poehler voiced the sweet and terrifying Granny in the "Have You Seen This Snail?" episode of SpongeBob SquarePants. Gary ran away from home, only to be found by Granny, who had a history of overfeeding and killing snails.

Jordan Fisher guest starred as Clark on the "iSpeed Date" episode of iCarly, where he participated in the speed-dating contest to take Carly to the school dance.

The Pretty Little Liars star appeared in the "Quinn's Date" episode of Zoey 101 as Candice, who Quinn tried to study for relationship advice.

You might recognize Janel Parrish from Pretty Little Liars or To All The Boys I've Loved Before, but before all that she guest starred as Sara in the "The Silver Hammer Society" episode of Zoey 101.

Also known for her role in Pretty Little Liars, Lucy Hale went on a date with Drake as Hazel in the "Theater Thug" episode of Drake & Josh. She also appeared in the "Upperclassmen & Gross Biology Dissection" episode of Ned's Declassified School Survival Guide as Amy (pictured above), the girl Moze's crush was trying to make jealous by asking Moze to be his date.

Supermodel Emily Ratajkowski guest starred as Gibby's girlfriend Tasha in the "iSpeed Date" and "iEnrage Gibby" episodes of iCarly.

High School Musical star and queen of Netflix Christmas movies Vanessa Hudgens guest starred as Rebecca — a girl who was kissed by Drake when she covered for his tardiness — in the "Little Sibling" episode of Drake & Josh.

Austin Butler guest starred in the "iLike Jake" episode of iCarly as Jake, who offered to perform on Carly's show but ended up being an awful singer.

The 13 Reasons Why star made a brief cameo in "The Demonator" episode of Drake & Josh, where he was dressed as a pirate.

Glee's Dianna Agron made an appearance in the "The Great Doheny" episode of Drake & Josh as Lexi, who went on a date with Drake.

The Glee and Shadowhunters star played Yûki — the host of a competing web show — in the "iGo to Japan" episode of iCarly. He also briefly appeared in the "Trading Places" episode of Zoey 101 as a waiter at Sushi Rox.

Jane Lynch, who also starred in Glee, made an appearance on iCarly as Sam's mom Pam Puckett in the "iSam's Mom" episode.

The La La Land star played Heather — a huge fan of Carly and the gang — in the "iFind Spencer Friends" episode of iCarly.

Star Wars star Mark Hamill voiced Mermaid Man's arch nemesis, the Moth, in four episodes of SpongeBob SquarePants. He first appears in the 2007 episode "Night Light."

Jim Parsons, who you might recognize from Big Bang Theory, guest starred in the "iLost My Mind" episode of iCarly as Caleb, who tried to convince Gibby he was from the year 2077 and needed to get back.

Beloved Jeopardy host Alex Trebek voiced Alan Quebec — the host of the fictional game show "Super Stumpers" — on Rugrats. He appeared in the 1993 "Game Show Didi/Toys in the Attic" episode.

Johnny Depp voiced the surfing legend Jack Kahuna Laguna in the 2011 episode of SpongeBob SquarePants called "SpongeBob SquarePants vs. The Big One." Jack helped SpongeBob and the crew get back to Bikini Bottom after they get pulled away to a distant island by a big wave.

Kesha appears as herself in the "Ice Cream For Ke$ha" episode of Victorious, where the gang tried to win a private concert by finding the letters that spell out "KE$HA" inside ice cream tubs. Kesha's little brother also made a cameo in the episode, as the little boy who found the last letter.

Jimmy Fallon and Tina Fey appeared as themselves in the "iShock America" episode of iCarly, in which they invited Carly and her friends to be on an episode of Late Night.

David Bowie voiced the Lord Royal Highness in the SpongeBob SquarePants musical special episode "Atlantis SquarePantis" in 2007.