Pizza in Japan...

After seeing edthethe's post about goya (bitter melon) and being reminded of how Japan uses it on pizzas (whyyyyyyy?!) it got me thinking about some of Japan's other interesting additions to one of my favorite foods. One of the first that came to mind is mentaiko - or roe. It's one of those additions that could be easy enough to mistake for your normal red/marinara sauce since it's that kind of color from a distance...do any expats actually like it?

Then there's the addition of corn on everything. I don't mind corn at all on it's own, but on pizza it just seems so unusual to me.

I've also heard of shirako (cod fish sperm) being used here as a pizza topping, but I thank my lucky stars everyday that I've never actually encountered it on a menu. 

Are there any unique pizza toppings you've stumbled across during your time in Japan that are in no way what you'd get back home? Any that you've liked? Hated? Were horrified by?!