It's a decent age for a cat. All that rigorous indolence and lasagne must have paid off. Garfield, that tiger-striped, sleepy-eyed, Monday-hating malcontent, most often seen tucked away in newspapers or suckered onto the windows of cars, turns 30 tomorrow. Happy birthday, Garfield.

June 19, 1978, is traditionally considered to be the birthday of Garfield (the cat) as well as Garfield (the comic strip), with strips noting his tenth birthday in 1988 and his 25th in 2003. Pedants may note that this would make Garfield exactly no days old on his first appearance, even though he looked fully-grown and was as sentient as he is now. It's best not to worry about this. Nobody ages in Garfield. The orange cat is the creation of cartoonist Jim Davis, whose own birthday (July 28) falls on the same day as that of Jon Arbuckle, Garfield's long-suffering owner. He and Garfield now appear in at least 2,570 newspapers and are read by about 263 million people every day- 4 per cent of the world's population. The idea, Davis once told The Washington Post, was “a conscious effort to come up with a marketable character”. He fools you by being sardonic and ginger, but Garfield's real strength is his inoffensiveness. In the 1980s, when those Garfield car toys were becoming ubiquitous, Davis stopped making them for five years. The business model, he says, is Snoopy. If nobody hates you, you never die. “I'm not overweight,” growls Garfield. “I'm undertall.” Or maybe: “You know it's Monday when you wake up on Tuesday.” Who could object to that?

How much is Garfield worth? In the strip, not so much. In reality, Paws Inc (Davis's company) has a higher turnover than some small countries. There is a Garfield Café in Malaysia, Garfield branded fruit, Garfield slot machines, and the Chinese use him to teach English. This week, a Manhattan judge decided to reduced the trust fund of Trouble, a small dog, by $10 million (£5 million). It will now inherit only $2 million from its late owner, the hotel boss Leona Helmsley. In 2004, the online magazine Slate.com estimated that Garfield-related merchandise generated between $750 million and $1 billion every year. Dogs lose.

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