well techniclly Sonny 2 is multiplayer you just need to get someone elses charachter code and you can play against him... not really multiplayer but thats whats its called
It doesn't matter how easy it is to hack a singleplayer game. The only time when it is a real issue is if there is some sort of global high score table or if the game is multiplayer. If people want to hack a game, then I'm ok with it as long as it doesn't mess with any global functions.