Jack is Oggy's cousin and the deuteragonist of the series.
Jack can be easily described as the opposite of Oggy. He's quick-tempered, violent, focused, self-important, sometimes lazy, nasty, and mechanic. More often than not, he's focused on getting rid of the cockroaches or doing something selfish. Jack often builds something to try and destroy the cockroaches, or any other insect that roams Oggy's house—and while he has had some success, more often than not his plans backfire. He also sometimes bullies Oggy, either moving him when he's in front of the TV, trying to beat Oggy in a race, or just going plain insane. He is perhaps the easiest target in the show, mainly because his rage gets him too unfocused on either getting rid of the cockroaches.
However at times, Jack can show his nicer side when he's not focused on stopping the cockroaches or acting villainous. He tends to play the "straight-man" to Oggy and the roaches' antics.
He is an olive green cat with a white tummy, yellow freckles, a sharp tail and hair coming out of his ears.
Jack owns a orange van that is mostly used in Drone Out of Control!. Jack owns a yellow safari jeep that is mostly used in Life's a Zoo. Throughout the series he mainly has a small green monster truck looking jeep, With flame paint jobs. He also had a Ferrari in The Pumpkin that Pretended to be a Ferrari.
Jack tends to be Oggy's partner in many episodes. Jack almost always helps Oggy when he's in trouble, whether it be from the cockroaches or getting stranded in space. Jack can be protective towards Oggy, as shown in "Flower-Power" "The Rise and the Fall". At times however, Jack's ego can get the better of him and will sometimes antagonize Oggy which usually ends with Oggy making peace with the cockroaches to stop him and give him what he deserves.
Jack does not like the cockroaches at all. While Oggy tends to have his positive moments with the cockroaches, Jack does not. He always goes after the roaches, even if they didn't do anything wrong. This is most notable in "Mayday! Mayday!" where after overcoming his sea sickness, he immediately crushes Joey and Marky despite them doing nothing wrong. However, this might be due to the cockroaches pulling off pranks that are often more painful and torturous than the ones Oggy usually receives.
Despite both of them being main characters of the show, they don't interact as often though their relationship seems to be positive in most episodes. However, they have interacted with each other in the Season 3 episode Formula 1 (Remake only).
Jack and Bob's relationship varies. Most of the time, Bob is annoyed by Jack and beats him up constantly. However, at times, they act like friends, most notably in Season 4.
Monica is Jack's love interest shown throughout Season 2. While they do love each other, Jack has immense trouble in expressing his love, mainly due to the Cockroaches' antics. Their relationship is far from perfect; as shown in "Sitcom" they tend to argue a lot. Their relationship seemingly ends in "Sky Diving". Jack has enough of her daredevil personality and eats her wedding ring, signifying that he no longer wants to marry her.