In the episode Mom-A-Geddon, we find out that he loves bumper cars.
It was shown in the episode Chilly Dog that Keswick has a passion for fish sticks, as he had an entire sack full of them.
In the episode Internal Affairs, he stated that he "really needed to start labeling his stuff."
Keswick has some slight features that resemble Timmy Turner from The Fairly OddParents. He is about the size of Timmy and he has the same buck teeth, but that is mostly because Butch Hartman created both T.U.F.F. Puppy and The Fairly OddParents.
In The Doomies, it shows that Keswick is not on good terms with his parents who wanted him to be a doctor instead of an inventor. In this episode, The Chief likes teasing him about this.
In Dog Dish, Keswick has a brother-in-law named Stan and seems to be on good terms with him. This also means that Keswick has a sister since he isn't married. He also seems to be in good terms with him.
In Thunder Dog, it shows that he is scared of girls and always jumps into the incinerator chute instead of the laundry shoot. Yet in every other episode, he's not afraid of girls.
In Snapnapped, he pictured himself tall, muscular, and smooth-talking which, is also known to be another hologram.
Keswick has made a total of seven named inventions in the show so far.
In Forget Me Mutt, we find out that Keswick is prone to motion sickness, which we can clearly see when he, Dudley, Kitty, and the Chief ride on the new Petropolis Monotrail.
In Dog's Best Friend, Keswick accidentally admits that he doesn't seem to enjoy working at T.U.F.F., and almost won enough money to get out of "this freak show."
In Watch Dog, it is a gag the fact that Keswick can invent only things which can shoot acid.
In Dudley Do-Wrong, it is shown that without regular social contact, Keswick becomes literally weird.
In Pup Daddy, we learn that as a teenager, Keswick had a tail and that when he grows out of it, the tails grows a new keswick, which had that two keswicks fight to the death. As a baby he looks like a fish with heat sensing fellers on his back.
In Toast of T.U.F.F. he does science at kids' birthday parties and left Billy in the 4th dimension as a result.
In Top Dog, he bluntly revealed to Dudley that his lasagna is not that good as it seems.
Ironically he's somewhat superstitious and can't make toilet paper thinking it comes from a wizard as revealed in Happy Howl-O-Ween.