Time travel, being a fictional concept, has no law saying it must be done via technology (sci-fi) or magic (fantasy).
Cameos don't bother me, nor do easter eggs. Because they are just that, cameos and easter eggs.
As for Twilight Princess being a ripoff of another werewolf game (I don't know what the other game is, Bloodmoon maybe?), lycanthropy has been around a lot longer than video games. Ripoff or not, I think the use of that concept is fair game.