Name's the Same: The British Dennis the Menace and the American Dennis the Menace. Same name, different clothes, completely different publisher and strip, independently conceived at the same time to within a week. The two are often confused. The British Dennis is several years older than the American and is more of an intentional mischief maker than his American counterpart. Indeed, the British Dennis is rather more like Bart Simpson than he is like the American Dennis.
Bart is, apparently, based on Dennis. You can see it in the shorts, catapult, spikey hair combination.