OK,OK, there's not a lot to tell. They are 'latch-key'cats, and when their owners go out to work, Zak and Bur get bored. So they either leap over the fence (flattening the poor old lilies) or else knock on the front door.
This is where the Tourettes Syndrome comes in, coz, if you don't open the door and let them in, they start bad-mouthing you. If Bur is in a stropy mood, he will leap from window-sill to window-sill until he is outside the first-floor bedroom window, and then yowl his head off.
The result is that rather than face the embarrasment of 'lace-curtain twitch' and tut-tutting neighbours (how could he do that to his cat, I'm going to the RSPCA immediately - serves him right if he ends up in a BBC fly-on-the-wall documentary about mistreating dumb animals, blah, blah, blah) you let him in. Big mistake as Zak like a shadow zooms in with him.
If cats were on drugs (and who knows what catnip really does to their brains) then Zak would have just got in from Kingston - no man not Hull - Jamaica! 'Like wow man far out, watch me do the perfect somersault down the landing stairs' - seems to be the only thing on his mind. Forget travelling overland to South Africa to find the perfect wave at Richards Bay - think bannisters!
Bur conversely is just back from from the Dome where he was clubbing with the Ministry of Sound, if ever they needed someone to replace Keanu Reeves in Speed III, he'd be your man. He is happiest when he is swatting bees. Picture the scene - the poor old bee has just loaded up with a cargo of genetically modified pollen, has been given clearance from Air Traffic Control and is about 3 feet up when 'zap' she is swatted onto terra firma.
Dazzed and confused the bee slowly staggers up, checks it's fuel-tanks, and is once again airborne, has cleared 4 foot, and whap, Bur runs 'amock', leaps into the air, claps his front-paws together, and down comes the bee, punch drunk as it it had gone 15 rounds with Mike Tyson. Fortunately the coup de grace is swift as it is flicked into the air, and swallowed. Exit Bur with a grin on his face and a strange buzzing noise in the pit of his stomach!