Grim will blatantly steal food and he seems unashamed of it, saying that “stolen food tastes way better” and “everything tastes better when it’s forbidden.”
Grim steals carpaccio from Jade’s plate during Halloween (“Food’s way more appetizing when it’s someone else’s”), tries to take an apple from the prefect, decides to take apples from a farmer when Epel tells him no, goes after the prefect’s ice cream during Glorious Masquerade, steals a doughnut from Ace, clam chowder during Port Fest and hints at wanting to steal jewelry from Leona.
Much like how Grim is quick to insult Leona, he also makes a comment during Vargas Camp about Vil’s club members running away because they are scared of him.
Vil replies, “I simply give warning when they don’t do their jobs.” Grim responds, “That’s still pretty harsh.”
Vil has a voice line about finding Grim’s fur on his school uniform.
Grim does not seem fond of Vargas, who apparently would have Grim and the prefect sit on a bench that he used as a dumbbell during Vargas Camp.
I have seen questions before about whether or not Grim is actively floating around the school, as he appears to be, but this might just be one of the ways the game is adapting to the limitations of the visual novel format:
Grim asks the prefect to hold him for a picture, Deuce has a line about him “trotting around underfoot” and Grim asks Cater to lower his phone so that he can see the screen, which all may insinuate that he might just be walking around
(He also has to jump up and down to be included in a picture during the White Rabbit Fes event)
Twisted Wonderland Reference Note 