While it sounds innocent enough, a “Wooden horse” is a medieval torture device on which you straddle the person you’re torturing. You can read more about it here (NSFW).
Disgaea 4 has…or rather, had…one of these. For reasons we aren’t entirely sure of, it was taken out. Here’s what originally existed in the game:
I…don’t think she’s quite using it the way it was intended to be used. Regardless, here’s what Nippon Ichi later changed the device to:
A much more innocent-looking…cat thing. Why? As we said, we’re not entirely sure, but we suspect it has to do with the game’s CERO rating in Japan. The CERO is like Japan’s ESRB, and so far, every Disgaea game has managed to squeeze by with an “A” (All-Ages) rating. For reference, Criminal Girls is a “D” (17 and up).
Perhaps Nippon Ichi felt — or were told — that the Wooden Horse would lead to a higher CERO rating. As we understand it, the distinction between the “A” and “B” (12 and up) ratings are the most strict, so perhaps that was what prompted the change.