1. Amy Poehler (SpongeBob SquarePants)
2. Jordan Fisher (iCarly)
3. Ashley Benson (Zoey 101)
4. Janel Parrish (Zoey 101)
5. Lucy Hale (Drake & Josh, Ned's Declassified School Survival Guide)
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.
6. Emily Ratajkowski (iCarly)
7. Vanessa Hudgens (Drake & Josh)
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.
8. Austin Butler (iCarly)
9. Dylan Minnette (Drake & Josh)
10. Dianna Agron (Drake & Josh)
11. Harry Shum, Jr (iCarly, Zoey 101)
12. Jane Lynch (iCarly)
13. Emma Stone (iCarly)
14. Mark Hamill (SpongeBob SquarePants)
15. Jim Parsons (iCarly)
16. Alex Trebek (Rugrats)
17. Johnny Depp (SpongeBob SquarePants)
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.
18. Ke$ha (Victorious)
Kesha appears as herself in the "Ice Cream For Ke$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.
19. Jimmy Fallon and Tina Fey (iCarly)
20. And finally, David Bowie (SpongeBob SquarePants)
David Bowie voiced the Lord Royal Highness in the SpongeBob SquarePants musical special episode "Atlantis SquarePantis" in 2007.