Throughout the show, many real animals were featured. Most of them were trained animal actors, taught by William Berloni and provided by his New York-based company Theatrical Animals. (source) This is a list of all the live-action animals that appeared on the show.
A red-bellied turtle is featured in the short "Guess!". In the short, Oobi hides the turtle in a box and asks Kako to guess what animal it is. He gives him four clues: legs, green, tail, and shell. Kako makes all kinds of wrong guesses, but when Oobi asks him to think harder, he realizes it must be a turtle. Oobi lifts the box, uncovering the turtle. They play with the turtle as the short ends.
A different turtle plays a main role in "Playdate!". In the episode, Oobi gets a turtle as a present. He invites Kako over for a playdate, but can't think about anything other than the turtle. He plays a turtle game, draws the turtle, and sings a song about the turtle. All the while, Kako gets more and more frustrated. He thinks that Oobi cares about the turtle more than him until Oobi apologizes. Kako has a change of heart, realizing that Oobi will always be his friend and was just excited to have a new pet.
The canary is the main focus of the short "Bird!". It seems to be Uma's pet, though it could just be someone else's pet that she is looking after. It lives in a big wooden birdcage with a perch and some toys.
In the short, Uma really wants to hear the canary sing, but it won't budge. She sings a tune, expecting the canary to chirp along, but it does nothing. She asks the viewers to sing with her, and the canary starts to chirp. Uma is ecstatic and sings for a while with it.
When Kako goes away for the day in "Kako's Puppy!", he asks Oobi to take care of his pet: a black-and-white Shih Tzu puppy. Oobi thinks the puppy is adorable and gladly accepts, thinking that he will do nothing but play with the puppy all day. He expects Grampu to help him puppy-sit; however, Grampu explains that it's Oobi's job to take care of the dog. Oobi realizes that pets are a big responsibility.
A hen appears in "Uma Chicken!". When Uma plays a farm animal game with Oobi and Kako, she becomes obsessed with acting like a chicken. She takes the game a little too far and refuses to do anything but cluck and eat seeds. Later, Uma hears a clucking noise outside and finds that it is a real hen, walking through her yard. She tries to play with it, but it doesn't even notice her. Bored with the hen, Uma decides that she would rather be herself.
"Petting Zoo!" features six real animals, the main one being a horse. The horse lives at the local petting zoo and loves to eat carrots. When Grampu takes Oobi and Kako to see the horse, they are nervous and don't want to go horseback riding. They decide to pet the other animals instead, but they get bored soon. They consider facing their fears of riding the horse, and Grampu shows them that the horse isn't scary by taking a ride himself. Oobi and Kako join him and pretend to be cowboys.
She was actually a Welsh mountain pony, not a normal horse. The crew wasn't able to use a regular-size horse because the hand puppet characters were too short to ride on top of one. The pony was trained by William Berloni and provided to the show in 2002. (source)
The pig is another animal at the petting zoo. Oobi and Kako think the pig is cute and imitate it by saying "Oink-oink" over and over again. Grampu lets Oobi pet the pig, and he's surprised that the pig is soft and hairy. Oobi and Kako notice a smell and ask if it's coming from Grampu. Embarrassed, Grampu says no, and they realize that it was coming from the pig.
The lamb is the last animal that Oobi and Kako see at the petting zoo. It lives in a wooden stable full of hay. When Oobi and Kako visit, they hear something making a loud "baa" noise and realize it's coming from the lamb. Grampu explains that the lamb is hungry and wants some food. Oobi and Kako take turns feeding it, and it happily eats from their palms.
In a game segment after the "Petting Zoo!" episode, Oobi is revealed to have a goldfish and a hamster as pets. Oobi and Kako play a memory game by guessing which of Oobi's pets will come next in a pattern. After the game, they decide to act like goldfish by pretending to swim around with their fingers.
Two ducklings make a very short appearance at the end of "Make Music!". Oobi and Grampu play a guessing game, but it's interrupted when they hear some peeping sounds. Oobi asks Grampu if he made the noise, and Grampu says "Not me." They look over and see Kako with a pair of ducklings. He says they're his "new band" and starts "peeping" along with them.
George is a guinea pig. He only appears in "Uma Preschool!" as the class pet of Paula's preschool class. Paula keeps him in a big cage at the center of her classroom. He can be heard making faint squeaking noises and eating hay. He is the only animal character on the show with an actual name.