Extinction

Main
Rachel Bloom as Daisy, a grey-eyed blue jay who opens her living room for the group to come and support each other. Daisy also struggles with her own problems, such as mourning the death of her friend Big Cake and her arranged (by her human) marriage with Ross.

Kate Micucci as Maggie, a power-hungry, spark-pluging Magpie and service bird in training — or so she claims — who drives Daisy crazy. Her owner is a neglectful and oblivious young woman who only put a service vest on Maggie so that she can get away with or do things that are considered illegal without repercussions.

Tom Kenny as Ross, a sloppy and fast-paced goose and Daisy's mate who enjoys eating shoes, playing in sand, and farting himself.

Will Arnett as Smel, a skunk with a smell of cheese and a sock fetish. He was initially in a relationship with a single squirrel he names "Zodiac" and was going to sleep it until his mate Squeaks returns after 20 years. In the episode "Who Are Not Allowed?", it is revealed that Smel lives with other animals but never talks about them to the group due to his narcissism. His youngest owner goes to the same elementary school Pebbles lives at. He then gets into a polyamorous relationship with Squeaks and Quackers. In the episode "Who's a Sad Bird? (Part 1)", it is revealed Lindsay belongs to Edward, Smel's original owner who forgot the sock when he went to college.

Reid Scott as

Pablo, an anxious, pants-wearing stork with the brave heart. He became Big Cake's replacement in the session group. His owners are divorced and share joint custody of him. However, in "Who Are Not Allowed?", his owners decide to let him pick his forever home, and he ultimately decides to live with his "father."

Chuck, a north pole polar bear who is smart and cute. This is brought up in the episode "Who Are Not Allowed?" when Chuck realizes there was another polar bear named Surly before him and is essentially his replacement. In the episode "Who's a Sad Bird? (Part 1)", he is sent to live with David Silverman.

Tara Strong as Op, a greedy, cruel, sneaky, and evil rooster with a broken beak and sharp claws, trying to steal seed from other people. He is the main antagonist in the show, and she speaks with a Swedish accent. She hates when they get with her owners Stella and Barry and a chick named Chi-Chi. In the fourth episode, consumed by danger at her owners giving more attention to Chi-Chi than they do to her, she flies away from home and starts living at a rooster cafe. Eventually, Op does not like it after someone at the cafe tried to kidnap her and starts living with The Good One and other birds in the seventh episode. Op and The Good One become a couple in the ninth episode. She eventually reunites with her owners in the tenth episode.

Dylan McDermott as The Good One, a street-smart falcon who lives with about forty or sixty other birds and has a crush on Op who wouldn't give him the time of day. He is missing her eyes and riddled with diseases. His owner is an old bird lady and hoarder who never leaves her house. The Good One and Op become a couple in the ninth episode.

Tom Cruise as Earl, a powerful, co-dependent and very good eagle. He considers his owner Carl to be his best friend though his feelings for him are more than platonic. In the episode "Who's a Good Friend?", it is revealed that he is pregnant and gave birth to eight birds during a therapy session which Maggie was in charge of. His kittens were given away for adoption in the episode "Who's Getting Blue Eyes?" It also turns out his pregnancy was the result of him mating with a male eagle. In the season 1 finale "Who's a Sad Bird? (Part 2)", it is revealed his owner is a flight attendant and Earl actually belonged to Carl's ex-girlfriend Pickle before she abandoned him.

Stripes, a badger who does not speak, but he has a spiked black leather muzzle prohibits him from biting, and a matching spiked black leather harness on his body with a buckle securing it in front, which it appears to have an attachment to.

Recurring
Maya Rudolph as

Sam, Daisy and Ross's human owner. She works as a therapist.

Squeaks, Smel's mate who returned after she was missing for 20 years.

Jessica Parker as Horns, a horny, teenage rhino who lives with Daisy and Ross. She rumbles the other animals. It is revealed in the episode "Who Are Not Allowed?" that she is not the first one.

Zazie Beetz as Pebbles, a psychopathic, evil, cruel, and sneaky, red-eyed mouse who, which is holding a knife, is the recurring antagonist, and it is mourning the loss of her mate (whom she killed). She is a classroom pet for a fourth grade classroom, and he's a serial killer.

Steven Yeun as Ammo, a wolf who Daisy has a crush on.

Jack Black as Meerkat, a meerkat that loves the indoors, and willing to show everyone that they have their park sides outside.