Ashley Johnson
Mirror Tulip "MT" (voice) (27 eps)
Owen Dennis
Sad-One (voice) (20 eps)
Jeremy Crutchley
Glad-One (voice) (15 eps)
Kirby
Grace (voice) (14 eps)
Kyle McCarley
Simon (voice) (13 eps)
Robbie Daymond
Jesse (voice) (13 eps)
Isabella Abiera
Hazel (voice) (10 eps)
Kate Mulgrew
The Cat (voice) (7 eps)
Ernie Hudson
Atticus (voice) (7 eps)
Ben Mendelsohn
Agent Mace (voice) (6 eps)
Bradley Whitford
Agent Sieve (voice) (5 eps)
Rhys Darby
Randall / Balloon Randall (voice) (3 eps)
Keith Ferguson
Comedy Mask (voice) (3 eps)
Justin Michael
Kevin / Soldier Turtle (voice) (3 eps)
Audrey Wasilewski
Megan Olsen (voice) (3 eps)
Dee Bradley Baker
Monster Atticus (voice) (3 eps)
Justin Felbinger
Nate (voice) (2 eps)
Reagan Gomez-Preston
Mikayla (voice) (2 eps)
Lindsay Katai
Little Badger Boy / Badger Mother (voice) (2 eps)
Matthew Rhys
Aloysius (voice) (2 eps)
Mark Fite
Andy Olsen (voice) (2 eps)
Lena Headey
The Conductor / Amelia (voice) (2 eps)
Jenna Davis
Lucy / Apex Child 3 / Apex Girl (voice) (2 eps)
Grey DeLisle
Lunch Lady / Tape Merchant / Seedy Merchant (voice) (1 eps)
Laraine Newman
Marietta Gillicutty / Maise Trundleshank (voice) (1 eps)
Kari Wahlgren
Sinesta Gillicutty / Bree Trundleshank / Girl Quadruplets (voice) (1 eps)
Rick Zieff
Ithmush Trundleshank / Nathaniel Trundleshank / Silas Trundleshank (voice) (1 eps)
Wayne Knight
Marcel (voice) (1 eps)
Scott Menville
Troy / Bully 1 (voice) (1 eps)
Bill Corbett
Perry the Parasite (voice) (1 eps)
BeBe Zahara Benet
Sashay (voice) (1 eps)
Naomi Hansen
5 Year Old Tulip (voice) (1 eps)
Lily Sanfelippo
6 Year Old Tulip / 8 Year Old Tulip (voice) (1 eps)
Ron Funches
Khaki Bottoms (voice) (1 eps)
Antonio Raul Corbo
Apex Child / Apex Child 2 (voice) (1 eps)
Alfred Molina
Chandelier (voice) (1 eps)
Jacob Farry
Apex Kid 2 (voice) (1 eps)