Ok, my quickest advice for this is to pop the guy on the nose...that is if he's still doing if after getting fixed. Usually a male cat's personality TOTALLY changes after getting fixed, and you might not have the problem again.
However, I happened to be blessed with a particularly rambunctious, fun-loving male (named Hobbes), and the thing that helped the best was bopping him on the nose or on the top of the head (and if it gets REALLY bad, flat out whopping him on the hind quarter...not enough to truly hurt him, but enough to give him the idea that it's not something tolerated in your house).
Now, if these things don't work, another idea is to get a spray bottle, fill it with water, and spray him when he does it (or anything else bad, for that matter). Might take a few times, but most cats really respond well to these things.
All else fails, ask your vet. :o)