1. Neil Patrick Harris as Prince Gumball
Of course, he sang.
2. Matthew Broderick as The Dream Warrior
Not even sure what's going here.
3. Mark Hamill as The Fear Feaster
Since portraying Luke Skywalker, Hamill's had a long and illustrious career as a voice actor, most notably his role as The Joker in Batman: The Animated Series.
4. Laura Silverman as Ethel Rainicorn
Silverman, sister of comedienne Sarah Silverman, plays the perfect doting mother.
5. George Takei as Ricardio the Heart Guy
Few do creepy better.
6. Henry Rollins as Bob Rainicorn
He also voiced this ill-tempered cookie man.
7. Andy Milonakis as Neptr
He even rapped.
8. Maria Bamford as Wildberry Princess
It was great seeing Bamford's signature dark humor in cartoon form.
9. Steve Little as Peppermint Butler
Little plays Stevie on Eastbound & Down.
10. Ron Perlman as The Lich
Appropriately enough the Hellboy star voices one of the show's scariest characters.
11. Miguel Ferrer as Death
You may remember Ferrer from his role on Twin Peaks as the cranky FBI Agent Albert Rosenfield.
12. Andy Samberg as Party Pat
Party Pat likes to, well, party.
13. Brian Baumgartner as Georgy
You may recognize Baumgartner as Kevin from The Office.
14. Donald Faison as Baby Snaps
The Scrubs star plays a heartbroken cookie.
15. M. Emmet Walsh as The Cosmic Owl
Walsh, one of the most revered character actors in Hollywood, participated in this epic beat box.
16. Toby Huss as Booboo
Huss is best known for playing Artie, the "Strongest Man in the World," on The Adventures of Pete & Pete.
17. "Weird" Al Yankovic as Banana Man
Yes, he sings.
18. Justin Roiland as The Earl of Lemongrab
Roiland is best known for his work on the animated show Fish Hooks. One of his biggest strengths is screaming.
19. Roz Ryan as Cake the Cat
Ryan also voiced Thalia in the Disney movie Hercules.
20. Paul Reubens as Ruler Gnome
The Pee-wee Herman star does a great supervillain.
21. Emo Phillips as Cuber
The kooky standup narrated the episode "Five Short Graybles."
22. Stephen Root as Grimby
Known for his role as Milton in Office Space, Root delivered this immortal line.
23. Kerri Kenney-Silver as Old Lady Princess
Kenney-Silver is best known for her role as Officer Wiegel on Reno 911!.
24. Brian Posehn as the Leader of the Businessmen
The standup comedian is best known for his role as "Brian" on The Sarah Silverman Program.
25. Michael Dorn as Gork
Audiences may recognize Dorn's deep voice from his role as Worf on Star Trek: The Next Generation.
26. Bobcat Goldthwait as Ed
27. Lou Ferrigno as Billy
You need big muscles to be this awesome.
28. Biz Markie as Snorlock
Only Biz could pull off this sexy jam.