I've set a protection on it that last for a week. Until then, keep it in a notepad or in the talk page of the article.
Also, note that it really doesn't matter who added it first. There is no "first" competition in Halopedia. So, people take credit for saying it first? Does it really matter? Do they actually gain something useful in their life for being first in getting information about a video game out (unless they're doing it for a living, then that's a different story)? It's a bad habit and simply childish/amateurish/immature. Instead, take the better approach by taking the "So, wut?" way.