In Mayday! Mayday! Jack is revealed to be seasick.

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.

Jack is shown to be afraid of monsters in 'Monster from the Mud Lagoon'.

Jack is known to have aerophobia in 'The Lighthouse Keeper', yet he isn't afraid of them when flying airplanes.

Jack will get seasick if he goes on a cruise ship, as shown in 'Mayday! Mayday!'.

He tends to play the 'straight-man' to Oggy and the roaches' antics. However, at times, Jack can show his nicer side when he's not focused on stopping the cockroaches or acting villainous. He is perhaps the easiest target in the show, mainly because his rage gets him too unfocused on either getting rid of the cockroaches. 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. 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. More often than not, he's focused on getting rid of the cockroaches or doing something selfish.

He's aggressive, focused, short-tempered, sometimes lazy, obnoxious, and mechanic. Jack can be easily described as the opposite of Oggy. He is an olive green cat with a red nose, pointed ears with hairs coming out of them, and a big head.

Oggy and the cockroaches full episode