It first aired on February 2, 2018.
Unikitty and the gang bring home a tiny creature they name Pet Pet, but Richard won't let them keep it if they can't prove they are responsible owners; when Pet Pet runs away, Unikitty must pretend to be Pet Pet until they can find him.
Unikitty and the gang bring home a tiny creature they name Pet Pet, but Richard won't let them keep it if they can't prove they are responsible owners. But when Pet Pet runs away, Unikitty must pretend to be Pet Pet until they can find him, or Richard will never let them have Pet Pet (or any pet) ever again! Will Unikitty survive pet training, or finally admit responsibility is a lot harder than she thought? 
During a trip to the forest, Unikitty, Puppycorn, Dr. Fox, Hawkodile, and Richard all take in the beauty of nature through a song. During the song, Unikitty notices a small yellow blob on the ground of the forests, stopping her thoughts. Dr. Fox comments that there are no members of its species anywhere to be found, concluding that it got left behind. Saddened, Unikitty hugs onto the blob, as it crumples up in a sneeze, which enamors Unikitty, Puppycorn, Dr. Fox, and Hawkodile. As the four of them gush over the blob, it reveals that it is able to talk, which enamors them further. Despite this, Richard points out that it does not belong to them, and pushes the princess away. Despite this, Unikitty and the others attempt to get Richard to let them take it home, which Richard protests to again, pointing out the previous times that Unikitty had brought home a pet.
Unikitty insists that this time will be different, but Richard refuses to budge, stating that he does not think Unikitty is responsible enough. Unikitty and the others agree to take care of the pet, while Richard eventually relents.
At the castle, Unikitty and the others attempt to think of a name for the new pet. Hawkodile suggests "Face Melter", Dr. Fox suggests "Test Subject", and Puppycorn suggests "Puppycorn". Unikitty ponders on a name, while the pet repeats what she says, turning it into "Pet Pet", a name she chooses. Richard squirts Pet Pet with a water bottle, claiming discipline, as pets are not allowed on the furniture. He then leaves to get pet insurance, instructing the others to train Pet Pet while he's gone. Once Richard leaves, the others quickly lose track of Pet Pet. They look through the castle, inadvertently destroying a majority of it in their search. When they hear Richard come back, they all hide, worried that they will be held responsible and never get to have a pet again. As Richard searches for the others, Unikitty sends Hawkodile out to find Pet Pet.
Grabbing a pillow and putting it over her as a disguise, Unikitty pretends to be Pet Pet, as she leads Richard back. Feigning surprise, Richard accepts that Unikitty is Pet Pet, asking if she made the mess. Squirting Unikitty with the squirt bottle, he instructs Dr. Fox and Puppycorn to take responsibility for Pet Pet. As Richard leaves, Dr. Fox questions what Unikitty is doing. The princess tells that she does not want Richard to know that they lost Pet Pet, so she plans to stall until Hawkodile finds Pet Pet, which she insists will not take too long.
Meanwhile, Hawkodile is in the kingdom, on the hunt for Pet Pet. Back at the castle, Richard runs through various tests for "Pet Pet" to go through, which Dr. Fox and Puppycorn instruct. Unikitty is able to make it through sitting, rolling over, and staying, but Puppycorn's command of a triple backflip corkscrew somersault proves too much for her. Using a high-caliber squirt bottle to punish "Pet Pet", Richard instructs Dr. Fox to do the same, as she does, despite Unikitty's protests. When Puppycorn brings up that Unikitty is not with them, Richard realizes the same, pointing out the whole thing was her idea. Acting quickly, Dr. Fox activates the "DoppelKitty", which summons one of her robots wearing a crude Unikitty mask. As Puppycorn leaves with the robot, Richard leaves to organize his record collection, demanding Pet Pet be better trained when he comes back. Despite Dr. Fox's protests, Unikitty insists on keeping the charade up until Hawkodile finds Pet Pet.
At the clover-topped citizen's house, she and her family are eating. Hawkodile suddenly bursts in, scaring them. Mistaking the muffin on the table for Pet Pet, he quickly jumps onto the table, only to realize his mistake. Eating the muffin, he leaps off of the table and out of the ceiling to continue his search.
Meanwhile, Unikitty continues to pretend to be Pet Pet. Her attempt to walk on a leash ends in her falling in a mud puddle. Her attempt to play fetch causes her to land in a spiky bush. She struggles through sled-pulling, tricks, dancing, eating pet food, and finally competing in a pet pageant, but she keeps the charade up. Richard admits to being impressed, but points out there is still one thing needed to make everything official.
At the Pets-A-Bunga pet store, Richard points out that Pet Pet needs to be "chipped, clipped, and snipped" to be a proper pet, as Richard leads the disguised Unikitty to the Chippy 3000. Unikitty finally snaps, admitting the truth of what happened to Pet Pet, preparing to face any punishment given. Richard admits that he is shocked that Unikitty was able to keep up the charade for so long, which surprises Unikitty. Richard comments that he is not mad at them, and believe that they are ready for a "real pet", something that confuses Unikitty.
Hawkodile then bursts in, carrying Pet Pet, who is scuffed up and not moving. He mentions that he found Pet Pet under the couch, and starts to mourn for him, only for another Pet Pet next to him to start mimicking him. Realizing that there is a whole barrel full of them, the others surround it, as Richard explains that Pet Pet is simply a toy that comes free with a bag of pet food at the store. He then reveals that the first Pet Pet simply got switched off, as he turns him back on, bringing him back to life. As they celebrate not being a failure, Unikitty happily celebrates Pet Pet, as Richard still insists that it is just a toy. Ignoring this, Unikitty asks if they can still keep Pet Pet, as Richard relents, stating they can all have one. As the others celebrate that they are great pet owners, Unikitty gives Richard a Pet Pet of his own, which mirrors his annoyed sigh.
For a full transcript of "Pet Pet", click here.