Cletus is a trained male police dog and a talented sniffer. He is able to sniff out a corpse and will bark to alert those in the area of any discovery. He is extremely fond of meat, particularly his bison dog treats. Sheriff Thompson dotes on Cletus, talking to him in baby talk and calling him his "best deputy," even as his actual deputy, Liv Baker, stands writing on a notepad "I hate Cletus."
Cletus a mixed-breed dog, possibly part French bulldog. He is small with mostly white fur, but with black fur around the mouth and nose. He is normally seen wearing a police vest.
Sheriff Mike Thompson and Deputy Liv Baker bring along Cletus when they come to investigate to the lake by Harry Vanderspeigle's cabin, hoping to find the body of a man whose foot was discovered earlier in the day by a fisherman trawling the lake. They are reluctantly joined by the town's mayor, Ben Hawthorne and his wife Kate Hawthorne. Ben argues that the whole affair is too expensive, commenting that the town won't be paying for snacks, then grabs a tin and starts eating from it, unaware that it actually contains Cletus's bison dog treats. Upon being told this, he spits one out, leading Thompson to chastise him for spitting out real bison meat.
The two groups split off to search the lake, but Cletus is left behind on the shore. The dog ends up finding Vanderspeigle's body washed up on the shore, only to be intercepted by the alien who has assumed Vanderspeigle's form and identity. Pursued by Cletus, he drags the body back to the lakeside cabin, hiding it in Vanderspeigle's own freezer. Later, Thompson and Baker return, having been forced to call off the search for the evening. Cletus begins barking wildly and leads the two directly to the freezer, but when the Vanderspeigle opens it, Thompson looks inside and sees a number of wrapped packages, one labeled "bison" and another labeled "pork chops." He concludes that the packages are the reason for Cletus's barking and declares that there's nothing else for them to do there. He, Baker and Cletus exit, leaving the Vanderspeigle alien to crow to himself over his victory.
Thopmson and Baker were busy sifting through evidence gathered from the lake in the office. Baker felt that a doorknob they had found might be significant, but Thompson dismissed her assertion, telling her that a houseboat was a type of boat and that a boat could sink. Therefore, it was perfectly normal to find a doorknob in a lake. He then commented "Cletus know that. Don't you boy?," speaking to the dog in baby talk and telling him that he was his favorite deputy and the best deputy in the world. As he continued with this, Baker scrawled on a notepad "I hate Cletus."
"The Green Glow"
Sheriff Thompson and Deputy Baker were in the office and Thompson told Baker that he could feel that they were going to solve the case of Dr. Sam Hodges's murder. He suggested that they might be put on Dateline, but when Baker expressed excitement at the possibility, Thompson clarified that he was talking about himself and Cletus, asking asking Cletus in baby talk "Do you want to be on the Dateline?" Asta Twelvetrees then visited the office, reporting that she believed it was her estranged husband Jimmy who stole one of the late Dr. Sam Hodges's prediction pads from the Patience Health Clinic. Thompson rocked a panting Cletus in his arms, saying that they had a lead.
Later, when Thompson and Baker were investigating a janitor at Patience's high school, Thompson expressed that he would feel better if Cletus was there, but that the "poor little guy" had a cold, so he set him up with a bed and a cup of tea. Baker replied that she was there and she was a human being, which wasn't too bad. The two managed to apprehend the janitor, Richard Ferguson, largely thanks to Baker's quick thinking, but Thompson was annoyed at Baker reading the guy his Miranda rights instead of allowing him to do it. When she met him the next day in the town diner to tell him that the paperwork had been completed, he chastised her for a lack of respect. This was the last straw for Baker. When a waitress arrived at the table with a to-go hamburger for Cletus, she took it herself, then pounded the bag, telling him that he was the one who had been disrespectful. When he told her that respect was earned, she replied that she quit, then took Cletus's to-go burger for herself, saying that it wasn't right to waste food.
- Resident Alien creator/executive producer Chris Sheridan stated that Cletus was created to "soften" the character of Mike Thompson and to show that while he comes across as strong-willed and, at times, cold, he nevertheless has a warmth and a capacity for love. He further stated that while viewers might expect Thompson to have a large German Shepherd, he felt it funny and a good character piece for him to have a smaller, cuter little dog.
- How Series From ‘B Positive’ to ‘Resident Alien’ Use Dogs to Define Characters by Danielle Turchiano. January 21, 2021