I'm new but I saw your question. The vet says the only fruits not to give are grapes and raisins - very toxic!
My old cat Lekky used to love cantalope and watermellon, and loved caned peas and corn. the Vet said it was fine as long as he didn't get too much and use it as a treat, just as Mrs_Savas says above. When Lekky was a kitten it was cute to hace him crawl up my overalls and take a bite from my hand - it stopprd being cute the first day he did it with no pants on(:
stretchycat
It is not uncommon for cats to eat fruit. Cantaloupe seems to be attractive to a fair number of cats, for some reason! But other fruits are too.
My only concern would be to keep an eye out to be sure that he doesn't develop diarrhea. Otherwise, let him have his treats - in some moderation :)