From the game guide:
“(Cater’s) hairstyle is not half-up, it is a pompadour. Snaggletooth character. His right canine tooth is generally visible. Drooping eyes. Both ears pierced.
His face looks a little older than that of Ace and Deuce, as he is a third-year student.
He tucks his hair over here behind his ear, so it curls forward. Look at the overall balance and give him something of a sexy look with the angle of the curl.”
Cater trying to convince Vil to let him upload a picture of Vil to Cater’s own Magicam is a theme throughout most of their interactions. Vil is unimpressed by Cater’s flatter (“I’d prefer you to keep that mouth shut if you have nothing genuine to say”) and refuses Cater’s constant requests for permission to share his photo.
When Cater is rejected by Eliza Vil responds with “I fail to see how your flippant chatter would spark anything but annoyance. Even the ghost was put off by your shallowness”, but Cater is undeterred, asking Vil for a picture during Beanfest, Vargas Camp 2 and wondering if he might be allowed one for his birthday.
They are the only two possessed that get paired together during Halloween, with possessed-Cater referring to Vil as “nuts” as possessed-Vil bemoans his own beauty.
Despite Vil’s lack of patience with Cater he still recommends him as “an expert on modern trends” for Fairy Gala.
During a vignette Cater says that he would like Vil to be his older brother, as Vil is independent, does things properly and might give him fashion tips or allow him to visit during photo shoots.
He also respects Vil’s ability to read the room, to understand what people are feeling without them having to say anything and to know exactly the emotional distance he should stay at without trying to get uncomfortably close or staying uncomfortably far away.
During the Firelit Sky event we learn that while Cater “always thought the Scalding Sands was a cool place”, he doesn’t “exactly have the money for vacations”, so he never expected to ever be able to actually visit.
Cater’s unique magic Split Card (In Japanese: Fluttering Hand (of Cards)) creates identical clones of Cater himself, though using the spell for an extended period of time is apparently very taxing.
It is unclear if there is a limit to how many copies Cater is capable of producing at one time. In-game he has only created four at once, but it has been hinted that he can do more, and he creates many at once in the manga.
It seems the copies might be capable of dying? In the manga we see one sacrifice itself to save Deuce during Riddle’s overblot.
Twisted Wonderland Reference Note 