When I look through this forum, I do not find any mod which add items or new creatures. Thats because it needs a client modification. So I have 3 guesses: Would be possible, but Bukkit does not allow to program that. Would not be possible because everyone needs the client update then. Wouldn't be possible. Even if everyone has Possibility 2 is interesting for me because when I play Lan i could give everyone the client modification
If I'm reading the question right... you're asking something like: "Can a bukkit plugin be written to be used in conjunction with a client modification to add things such as custom mobs or items?" The answer is yes it is possible. Someone is working on a project similar to what you're asking for in the development section.
cool wow, do you have the link? And... Does everyone has to inject it to their own minecraft? Ty for help! EDIT: Do you mean Aeron's thread?
WorldEdit has a client mod, for instance By the way, Bukkit is a minecraft server, not a client, that's why server plugins are supposed to be discussed in the "Bukkit -> Plugin Requests". EDIT by Moderator: merged posts, please use the edit button instead of double posting.