Favorite minor trend in a game series

[Psychospacecow]

Since we're on a roll with these apparently, what's a little in-joke or common theme that each game in a series has that you like? It doesn't have to be big, in fact it shouldn't be big in this thread, but its there.

For example:
In every Pokemon game, there is a fan man in the main character's home town who talks about how amazing technology is, describing how one can interact with others in the game.