Jack is Oggy's cousin and the deuteragonist of the series. He is an olive green cat with a red nose, pointed ears with hairs coming out of them and a big head.
Jack can be easily described as the opposite of Oggy. He's aggressive, focused, short-tempered, sometimes lazy, obnoxious 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.
- Jack will get seasick if he goes on a cruise ship, as shown in "Mayday! Mayday!" and "A Dreamy Cruise".
- Jack is known to have acrophobia in "The Lighthouse Keeper", but was not in The Rise and the Fall and Vertigo! however.
- Jack is shown to be afraid of monsters in "Monster from the Mud Lagoon" and "Good Night, Don't Sleep Tight".
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" and "Zen Oggy" "The Rise and the Fall" and "Vertigo!". At times however, Jack's ego can get the better of him and will sometimes antagonize Oggy.
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!" and "A Dreamy Cruise" 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.
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" and "The Laugh Box", they tend to argue a lot. Their relationship seemingly ends in "Sky Diving" and "Freefall Jump". Jack has enough of her daredevil personality and eats her wedding ring, signifying that he no longer wants to marry her.
Jack is a real time bomb on four paws. He is naturally aggressive and totally impulsive. He has decided to turn Oggy, his pampered, comfy, bourgeois cousin, into a cat, a real cat! Jack is the ideal witness to all of the horrors that the roaches inflict on Oggy. And he is always there to pick up his cousin's pieces.
Cartoon Network Asia
One thing you can say about Jack, he's not given over to self-doubt. As keyed up as an over-wound alarm clock, Jack is quick to take affront. What's more, he suffers from abnormally high blood pressure. In other words, he could explode at any moment.
Disney Channel Asia
Other cat in the show. He is Oggy's cousin and a complete opposite of Oggy; Jack is short-tempered, violent, arrogant - a perfect target for the roaches to annoy. He often finds himself building huge machinery such as roach-catching contraptions, most of the time resulting in backfiring. He is also very interested in chemistry. Jack is Oggy's very close friend and neighbour.
- Jack, being Oggy's cousin, could very likely reference the real life shop Cousin Jack's Pasty Co., where it sells cornish pasties, and "Oggy" is also an alternate name for cornish pasties.
- In Mayday! Mayday! and A Dreamy Cruise, Jack is revealed to be seasick. However, in Castaway Cats he never shows any signs of being seasick.
- Jack's residency is inconsistent. In some episodes, he lives in his own house and usually visits Oggy, while in other episodes, he'd be roommates with Oggy. This has stopped in Season 4, where Jack has been given a permanent house.
- Then again, being from a comedy show, this inconsistency might be for comedic purposes.
- Even though Jack's home is next to Oggy's, he'll always ride in his jeep instead of walking.
- Jack has the 5th largest amount of appearances in the show, behind Oggy, Marky, Joey, and Dee Dee.
- Despite not being the most abused character in the show (due to not appearing in all episodes), the gags pulled on Jack are usually more violent and/or nasty than the ones pulled on Oggy.
- Jack is the only main character to have more losses than victories in every season.
- Jack is similar to Sylvester from Looney Tunes and Top Cat.