Grudge
Grudge was a large cat owned by Cleveland Booker in the 3180s and 3190s. According to Booker, her size was due to a thyroid condition.

Booker told Michael Burnham that Grudge was so named "because she's heavy, and all mine."

Booker was defensive of Grudge and her name. When Cosmo Traitt threatened to "roast Grudge and feed her to the starving" (adding that she would feed a planet), Book told Traitt to keep Grudge's name out of his mouth and called Grudge "a queen." () Book apparently called Grudge a queen frequently enough that Burnham teased him about it. ()

Grudge, along with Book and his vessel, traveled to Earth with Discovery and remained in the region afterward. () About a month later, after Discovery reunited with Starfleet command, Booker's ship arrived unexpectedly with only Grudge aboard. The crew discovered he was exploring a lead on a black box and had set his ship to deliver Grudge to Discovery if he was detained. Burnham left Grudge in her shared quarters with Ensign Sylvia Tilly, who was wary of the animal's size, before departing on Booker's ship on a rescue mission. Grudge was fitted with a collar with an embedded tracking device.  was of the opinion, however, that the cat could never get lost, that she had her own gravitational pull. ()

When Lieutenant Detmer and Ryn took Booker's ship into battle against the Emerald Chain flagship Viridian, Grudge leapt onto Ryn's lap, much to the Andorian's alarm as he had never see a cat before. ()

Grudge accompanied Booker on his initial exploration of the Verubin Nebula, where they were exposed to significant radiation. After emerging, both were successfully treated with DNA recombination. However, Booker noted that Grudge had been favoring her left front paw, and Dr. Tracy Pollard agreed to examine her further. ()

Grudge was aboard Booker's ship when he crash landed it into Discoverys shuttlebay as Osyraa piloted it into the Federation's distortion field. Before he and Burnham left to retake Discovery, Booker noted Grudge was "safe and secure" aboard his ship. () Later, as Booker and Zareh fought aboard an open turbolift car, Zareh mockingly asked Booker whether he or "that fat cat of yours" would leave a larger stain from a fall. Booker overcame Zareh and threw him to his death instead, shouting after him, "She's… a queen!" ()

Grudge had an aversion towards holograms as she could not smell them. ()

Appendices

Background information
Grudge was created by writer/producer Jenny Lumet. Lumet based Grudge on a  dog, Nelly, that belonged to her grandmother, . Horne used to keep Nelly in the sleeve of her kimono. According to Lumet, Nelly "never did anything." 

Grudge was portrayed by  brothers Leeu and Durban.  The Maine Coon is a naturally large breed of cat, whose weight ranges from 13-18 lbs in their adulthood. Leeu weighed about 18lb when filming of season 3 began.

External link 
 
Cats