Clyde was previously owned by Len Pontecorvo who Holmes knew from a conspiracy theory forum. Holmes and Watson discover Len is dead so Holmes takes Clyde to The Brownstone. Holmes leads Watson to believe that he will make soup out of Clyde, but later, reveals he admires tortoises.
|Clyde makes his first appearance at 5:55 in his terrarium at Len Pontecorvo's home. Holmes takes him home in order that he won't starve to death. Holmes finds a listening device hidden in a fake rock in Clyde's terrarium leading him to believe that Len's paranoia may be justified. ("The Red Team") At 35:22, Holmes uses Clyde to represent an ambulance on a map of New York City in order to deduce how a real ambulance evaded a series of road blocks during a winter storm. ("Snow Angels")|
|At 13:58, Watson is woken by a lettuce eating Clyde whom Holmes has put on her bed to wake her. Holmes is endevouring to be a more considerate flat mate and believes this manner of waking Watson to be polite. Watson brings Clyde downstairs to his terrarium. ("We Are Everyone") At 22:00, as a distraction from the case of who murdered Rada Hollingsworth, Holmes sees which items in the Brownstone are lighter or heavier than Clyde. ("Tremors") At 28:27, Holmes uses Clyde to wake Watson up. Clyde is wearing a blue "turtle cozy" that looks like a shark fin knitted for him by Ms. Hudson. At 39:15, he wakes her again with Clyde who is wearing a different cozy with a note that says "Have you seen what's on TV?". ("The Many Mouths of Aaron Colville")|
|After Holmes abruptly leaves for England, Clyde is seen being cared for by Watson at her apartment at 4:03. ("Enough Nemesis To Go Around") At the episode beginning, Clyde is eating lettuce while Kitty complains to Holmes that she won't take Clyde to Watson's apartment in Chelsea. Holmes indicates that Clyde resides with him on weekends and with Watson on weekdays. ("Bella") At 1:04, Clyde is taking part in an experiment with Kitty in which he presses a lever to shock her or to get food. Holmes wants to find out if reptiles can display empathy but warns Kitty that Clyde may want her to be harmed. ("Rip Off") At the episode start, Kitty talks to Watson about taking care of Clyde while Watson was in Copenhagen with Andrew. ("Terra Pericolosa")|
|At 29:11, Clyde paints a canvas on the floor using a device Holmes has attached to his back while Watson discusses meeting Andrew's father and realizes she doesn't want a normal relationship. ("Hemlock") At 10:10, Clyde is seen eating lettuce and listening to music Holmes is playing while trying to determine the identity of Everyone member "Sucking Chest Wound". Holmes catalogues the songs Clyde likes and dislikes. ("One Watson, One Holmes") At 23:03, Clyde is seen eating lettuce from a plate in the centre of the kitchen table while Holmes reviews plant manuscripts. ("Under My Skin") His terrarium, with the light on, is in Watson's office in the Brownstone basement at 24:20. ("Absconded")|
|At 0:45, Holmes is seen cooking snacks for Clyde to help increase his mineral intake. At 14:23, Clyde is seen in his terrarium beside Holmes while he works on a computer. Watson comments that Clyde is enjoying the snacks Holmes made and may also be enjoying his "dinner date" since Holmes is dressed in a tuxedo. Holmes indicates that his dinner date is his father, Morland Holmes and compares his father to Clyde as both are "cold blooded reptiles". ("Tag, You're Me") At the episode beginning, Watson discovers a box in the refrigerator containing Clyde who Holmes has placed there to hibernate. Clyde usually hibernates in a burrow in the back yard but Holmes considers New York winter's climate too unpredictable. ("Murder Ex Machina") At 36:42, Clyde has emerged from hibernation and is in his terrarium while Holmes does hot yoga. ("Hounded") At 26:20, Lin Wen says she likes Clyde but he isn't seen. ("All In")|
|At 27:10, Watson is seen chopping vegetables and then feeds Clyde as she and Holmes discuss their case. ("Worth Several Cities") At 36:02, Clyde is seen crawling on the floor as Holmes has placed a venomous snake in his terrarium. ("Ill Tidings") At 0:35, Clyde eats lettuce while Lin Wen compliments Watson on her scallion pancakes. ("Bang Bang Shoot Chute")|
|In the wake of Mycroft's death, Morland visits the Brownstone and handles Clyde. He discusses Clyde's age and who will care for him once Sherlock dies. ("The Adventures of Ersatz Sobekneferu") Holmes and Watson file Clyde's claws while listening to music to calm Watson as tortoises have terrible hearing. ("Through the Fog")|
- Clyde is played by two Russian tortoises, which are rotated out after each take.
- Music Clyde likes includes Brahms and Goatwhore. He doesn't like Tyler Swift. ("One Watson, One Holmes")
- Watson unknowingly eats soup from one of the bowls used for Clyde's baths. Holmes uses Clyde's DNA as one of several samples to have a lab honestly match crime scene DNA to. ("Art Imitates Art")
- Kitty has agreed to take Clyde once Holmes and Watson die. Her son Archie will take him after Kitty dies. ("The Adventures of Ersatz Sobekneferu")
- "I hereby forego my right to tell my nonexistent friends that I am pet-sitting a sociopathic tortoise."
- ―Kitty, "Rip Off".
- "Well, my partner puts wool cozies on our tortoise. You're not even approaching weird."
- ―Watson, "You've Come a Long Way, Baby".