- Paul Reubens - Gnome Ruler/Dancing Bug (voice)
- Emo Philips - Cuber (voice)
- Billy West - Goose / Erik Adamkinson / Mayor (voice)
- Ava Acres - Young Marceline (voice)
- Ava Acres - Candy Girl
- Ava Acres - Candy Kids (voice)
- Ava Acres - Sunshine / Jamaica (voice)
- Ava Acres - Young Marceline / Bunny Girl (voice)
- Ava Acres - Jamaica (voice)
- Ashly Burch - Breezy (voice)
- Ashly Burch - Blacksmith / Scorpion (voice)
- Ashly Burch - Celina / Cheryl (voice)
- Ashly Burch - Cheryl / Celina / Super Porp Mutant (voice)
- Brian Doyle-Murray - Prince Huge
- Alan Oppenheimer - Darren the Ancient Sleeper/Sun (voice)
- Beau Billingslea - The Moon (voice)
- Eric Bauza - Buttersotch Butler (voice)
- Kyla Rae Kowalewski - Me-Mow
- Willow Smith - Beth (voice)
- Sean Giambrone - Shermy (voice)
- Brian Baumgartner - Georgy / Private
- Toby Huss - Booboo / Commander
- Kevin Michael Richardson - Donny
- Kevin Michael Richardson - The Storm
- 'Weird Al' Yankovic - Banana Man
- James Urbaniak - Rat King / Leaf Beard
- James Urbaniak - Vice President Blowfish
- Thurop Van Orman - Tree Witch
- Thurop Van Orman - Kent
- George Takei - Ricardio
- Andy Milonakis - Neptr
- Andy Samberg - Party Splat
- Andy Samberg - Party Pat / Rap Bear
- Andy Samberg - Party Pat
- Neil Patrick Harris - Prince Gumball
- Hannibal Buress - Flame Prince
- Donald Glover - Marshall Lee
- Crispin Freeman - Turtle Prince
- Grey DeLisle - Ice Queen
- Peter Serafinowicz - Lumpy Space Prince
- Madeleine Martin - Fionna
- Elle Newlands - Butterscotch Butler
- Matthew Broderick - Dream Warrior
- Mark Hamill - Dark Magician (voice)
- Ako Castuera - Canyon
- Bert Youn - Lee
- Laura Silverman - Ethel Rainicorn
- Fred Stoller - Roy
- John Hodgman - DJ Plop Drops
- John Hodgman - Elder Plops
- Kate Micucci - Chips (voice)
- Kate Micucci - Wendy
- Donald Faison - Princess Cookie
- M. Emmet Walsh - Cosmic Owl
- Kay Lenz - Bird Woman
- Kumail Nanjiani - Prismo (voice)
- Kent Osborne - Bounce House Princess
- Kent Osborne - Additional Voices (voice)
- Lou Ferrigno - Billy
- Dee Bradley Baker - Mr. Cream Puff / Mr. Cupcake / Chet (voice)
- Maria Bamford - Manfried / Chocoberry / Candy Corn Girl (voice)
- Henry Rollins - Bob Rainicorn
- Henry Rollins - Cookie (voice)
- Mark Proksch - Johnnie
- Justin Roiland - Earl of Lemongrab (voice)
- Justin Roiland - Earl of Lemongrab (voice) / Lemongrab 2 (voice)
- Justin Roiland - Lemonpink (voice)
- Justin Roiland - Lemonpink (voice) / Gummy Fish (voice)
- Justin Roiland - Earl of Lemongrab (voice) / Starfish Martian (voice)
- Roz Ryan - Cake
- Marc Maron - Squirrel
- LeVar Burton - Bubble (voice)
- Kristen Schaal - Jake Jr (voice)
- Kristen Schaal - Jack Jr (voice)
- Melissa Villaseñor - Clerk (voice)
- Dan Mintz - Tv (voice)
- Riki Lindhome - Island Lady (voice)
- Riki Lindhome - Ice Cream (voice)
- Lucy Lawless - General Tarsal (voice)
- Alia Shawkat - Betsy (voice)
- Sharon Horgan - Minerva (voice)
- Steve Little - Abracadaniel (voice)
- Steve Little - Zombie Candy Heart / Peppermint Butler / Gumball Guardian #2 (voice)
- Chelsea Peretti - Queen of Ooo (voice)
- Jackie Buscarino - Eclair Boy (voice)
- Jackie Buscarino - Susan Strong / Kara / Additional Voices (voice)
- Jenny Slate - Huntress Wizard (voice)
- Paul Scheer - Toronto (voice)
- Dave Foley - Warren Ampersand (voice)
- Felicia Day - Betty (voice)
- James Baxter - James Baxter
- Keith David - Balthus (voice)
- Keith David - Flame King (voice)
- J.G. Quintel - Blue Jay (voice)
- John Moschitta Jr. - Key-per (voice)
- Sam Marin - Gareth / Flying Lettuce Brother (voice)
- Collin Dean - Tiffany (voice)
- Cole Sanchez - Party God (voice)
- Maurice LaMarche - Grand Master Wizard (voice)
- Maurice LaMarche - Wizard Police (voice)
- Steve Agee - Ash (voice)
- Martin Olson - Hunson Abadeer (voice)
- Alan Tudyk - Chatsberry (voice)
- Pamela Adlon - Gunther (voice)
- Lauren Lapkus - Patience St. Pim (voice)
- Creed Bratton - Phlannel Boxingday (voice)
- Open Mike Eagle - Gingerbread Rapper / Rapper Chipmunk (voice)
- Stephen Root - Martin (voice)
- Laraine Newman - Widow / Additional Voices (voice)
- Lennon Parham - Additional Voices (voice)
- Livvy Stubenrauch - Young Kara (voice)
- Livvy Stubenrauch - Bonnibel (voice)
- Pendleton Ward
- Thurop Van Orman
Mark Hamill interpreta a Dark Magician (voice) en la serie.
M. Emmet Walsh interpreta a Cosmic Owl en la serie.
LeVar Burton interpreta a Bubble (voice) en la serie.
Matthew Broderick hace el papel de Dream Warrior.
Riki Lindhome hace el papel de Ice Cream (voice).
George Takei interpreta a Ricardio en la serie.
Brian Doyle-Murray interpreta a Prince Huge en la serie.
Jeremy Shada interpreta a Finn the Human (voice) en la serie.
John DiMaggio hace el papel de Jake the Dog (voice).
Tom Kenny hace el papel de Ice King (voice).
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